Abstract:
The present disclosure provides a semiconductor device including: a semiconductor identifier holding portion configured to hold a semiconductor identifier for identifying a semiconductor device; and a control portion configured such that upon elapse of a predetermined time period following receipt of an externally input instruction to hold the semiconductor identifier, the control portion issues an instruction to the semiconductor device immediately downstream of the semiconductor device to hold a semiconductor identifier of the immediately downstream semiconductor device and that during the time period between the point in time at which the externally input instruction is received and the point in time at which the instruction is issued to the immediately downstream semiconductor device to hold the semiconductor identifier thereof, the control portion causes the semiconductor identifier holding portion to hold the externally input identifier.

Description:
BACKGROUND 
     The present disclosure relates to a semiconductor device and an integrated semiconductor device. More particularly, the disclosure relates to a semiconductor device and an integrated semiconductor device having a circuit structure for supporting tests at the time of manufacture. 
     The integrated semiconductor device such as a multilayer semiconductor device formed by stacking semiconductor chips in multiple layers has a plurality of chip selection terminals for individually controlling the semiconductor chips configured. In many cases, a suitable number of these chip selection terminals are provided to address the layered semiconductor chips. It may thus be necessary to increase the number of chip selection terminals in proportion to a growing number of semiconductor chips in layers. 
     Techniques have been known to determine which of the multiple chip selection terminals to use on the semiconductor device. On such technique involves providing each of the chips with a unique chip ID and using fuse trimming so as to control the chips individually (e.g., see Japanese Patent Laid-Open No. 2005-122823 (FIG. 3)). 
     SUMMARY 
     According to the above-cited technique, once a chip ID is assigned to a given semiconductor chip, the relation between the chip ID and the corresponding chip selection terminal remains unchanged. This can entail the following problem at the manufacturing stage: a multilayer semiconductor device under test has its layered chip semiconductor devices measured individually. In this case, the test device in use may need as many terminals as the number of chip selection terminals for chip selection. Given the fact that multilayer semiconductor devices are mass-produced, it may be necessary for each test device to test simultaneously as many multilayer semiconductor devices as possible. However, since the number of terminals on the test device is finite, if it is desired to increase the number of multilayer semiconductor devices to be tested simultaneously, then there is no choice but to reduce the number of those terminals on the test device which can be assigned to a single multilayer semiconductor device. This can give rise to the situation where it is difficult for the test device to assign its terminals to all chip selection terminals typically at the time of testing. However, if the number of terminals to be assigned to the chip selection terminals is limited, then all semiconductor chips constituting the multilayer semiconductor device may not be measured. For example, suppose that the test device has only one terminal to be assigned to chip selection terminals. Each of the chip selection terminals corresponds to each of the semiconductor chips in the multilayer semiconductor device. It follows that the test device can control only one semiconductor chip corresponding to the chip selection terminal connected to the assigned terminal. That is, only that one semiconductor chip can be tested in this case. 
     The present disclosure has been made in view of the above circumstances and provides arrangements for reducing the number of those terminals on the test device which are assigned to chip selection terminals on the assumption that all semiconductor chips making up the integrated semiconductor device are to be tested. 
     According to one embodiment of the present disclosure, there is provided a semiconductor device including: a semiconductor identifier holding portion configured to hold a semiconductor identifier for identifying a semiconductor device; and a control portion configured such that upon elapse of a predetermined time period following receipt of an externally input instruction to hold the semiconductor identifier, the control portion issues an instruction to the semiconductor device immediately downstream of this semiconductor device to hold a semiconductor identifier of the immediately downstream semiconductor device and that during the time period between the point in time at which the externally input instruction is received and the point in time at which the instruction is issued to the immediately downstream semiconductor device to hold the semiconductor identifier thereof, the control portion causes the semiconductor identifier holding portion to hold the externally input identifier. This structure provides the function of holding the semiconductor identifier in response to the externally input instruction to hold the semiconductor identifier while instructing the immediately downstream semiconductor device to hold the semiconductor identifier thereof. 
     Preferably, the semiconductor device may further include a signal selection portion configured such that when, of a plurality of semiconductor device selection signals-input in correspondence with the semiconductor identifiers for selectively controlling semiconductor devices, the semiconductor device selection signal corresponding to the semiconductor identifier held in the semiconductor device identifier holding portion is enabled, the signal selection portion may enable internal circuits of the semiconductor device corresponding to the semiconductor identifier being held. This structure provides the function of allowing the semiconductor device to operate assuming that the semiconductor identifier thereof is being held in the semiconductor identifier holding portion. 
     Preferably, upon elapse of a predetermined time period following stop of the externally input instruction to hold the semiconductor identifier, the control portion may stop the instruction issued to the immediately downstream semiconductor device to hold the semiconductor identifier thereof; and during the time period between the point in time at which the externally input instruction to hold the semiconductor identifier is stopped and the point in time at which the instruction issued to the immediately downstream semiconductor device to hold the semiconductor identifier thereof is stopped, the control portion may cause the semiconductor identifier holding portion to reset the semiconductor identifier being held. This structure provides the function of resetting the semiconductor identifier in response to a stop of the externally input instruction to hold the semiconductor identifier while instructing the immediately downstream semiconductor device to reset the semiconductor identifier thereof. 
     Preferably, upon input of a hold command instructing the semiconductor identifier to be held, the control portion may instruct the immediately downstream semiconductor device to hold the semiconductor identifier thereof upon elapse of a predetermined time period following input of the hold command; and during the time period between the point in time at which the hold command is input and the point in time at which the immediately downstream semiconductor device is instructed to hold the semiconductor identifier thereof, the control portion may cause the semiconductor identifier holding portion to hold the semiconductor identifier. This structure provides the function of holding the semiconductor identifier in response to the hold command while instructing the immediately downstream semiconductor device to hold the semiconductor identifier thereof. 
     Preferably, the semiconductor device of the present disclosure may further include a fixed semiconductor identifier holding portion configured to hold a fixed semiconductor identifier corresponding to the semiconductor device; and only if, of a plurality of semiconductor device selection signals input in correspondence with the semiconductor identifiers for selectively controlling semiconductor devices, the semiconductor device selection signal corresponding to the fixed semiconductor identifier is enabled, may the control portion instruct the immediately downstream semiconductor device to hold the semiconductor identifier thereof and cause the semiconductor identifier holding portion to hold the semiconductor identifier. This structure provides the function of causing one of serially connected semiconductor devices of which the semiconductor device selection signal is enabled corresponding to the semiconductor identifier matching the fixed semiconductor identifier, to operate in response to the hold command. 
     Preferably, upon input of a reset command instructing the semiconductor identifier to be reset, the control portion may instruct the semiconductor device immediately preceding this semiconductor device to reset the semiconductor identifier of the immediately preceding semiconductor device. This structure provides the function of instructing the immediately preceding semiconductor device to reset the semiconductor identifier thereof. 
     Preferably, given an instruction from the immediately downstream semiconductor device to reset the semiconductor identifier, the control portion may instruct the immediately preceding semiconductor device to reset the semiconductor identifier thereof. This structure provides the function of allowing the immediately downstream semiconductor device to instruct the current semiconductor device to reset the semiconductor identifier thereof. 
     Preferably, upon receipt of an instruction to reset the semiconductor identifier while the immediately downstream semiconductor device is being instructed to hold the semiconductor identifier thereof in response to the input of the hold command, the control portion may stop the instruction to the immediately downstream semiconductor device to hold the semiconductor identifier thereof upon elapse of a predetermined time period following receipt of the instruction to reset the semiconductor identifier; and during the time period between the point in time at which the instruction to reset the semiconductor identifier is received and the point in time at which the instruction to the immediately downstream semiconductor device to hold the semiconductor identifier thereof is stopped, the control portion may reset the semiconductor identifier being held in the semiconductor identifier holding portion. This structure provides the function of allowing the semiconductor device having operated in response to the hold command to operate in response to the reset command. 
     According to another embodiment of the present disclosure, there is provided an integrated semiconductor device including a plurality of semiconductor devices, each of the semiconductor devices including: a semiconductor identifier holding portion configured to hold a semiconductor identifier for identifying a semiconductor device; and a control portion configured such that upon elapse of a predetermined time period following receipt of an externally input instruction to hold the semiconductor identifier, the control portion issues an instruction to the semiconductor device immediately downstream of the semiconductor device to hold a semiconductor identifier of the immediately downstream semiconductor device and that during the time period between the point in time at which the externally input instruction is received and the point in time at which the instruction is issued to the immediately downstream semiconductor device to hold the semiconductor identifier thereof, the control portion causes the semiconductor identifier holding portion to hold the externally input identifiers issued parallelly to all of the plurality of semiconductor devices. This structure provides the function of allowing each of the semiconductor devices making up the integrated semiconductor device to hold the semiconductor identifier of the semiconductor device in question in accordance with the externally input instruction to hold the semiconductor identifier while instructing the immediately downstream semiconductor device to hold the semiconductor identifier thereof. 
     According to the present disclosure outlined above, a desired semiconductor identifier can be set to each of the semiconductor devices constituting the integrated semiconductor device in accordance with the semiconductor identifier designated by an externally input semiconductor identifier designation signal. This arrangement makes it possible for the test device to control each semiconductor device using a single semiconductor identifier. That in turn provides the effect of reducing the number of terminals to be assigned to the chip selection terminals on the test device on the assumption that all semiconductor devices making up each integrated semiconductor device are to be tested. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a typical structure of an integrated semiconductor device as a first embodiment of the present disclosure; 
         FIG. 2  is a schematic view showing a typical structure of the integrated semiconductor device of the multilayer type as the first embodiment; 
         FIG. 3  is a schematic view showing a typical test environment for the integrated semiconductor device as the first embodiment; 
         FIG. 4  is a timing chart showing typical operation timings corresponding to the chip identifiers being set of a 0th chip through a third chip in the first embodiment; 
         FIG. 5  is a timing chart showing typical operation timings corresponding to the chip identifiers being reset of the 0th chip through the third chip in the first embodiment; 
         FIG. 6  is a schematic view showing a typical structure of an integrated semiconductor device as a second embodiment of the present disclosure; 
         FIG. 7  is a schematic view showing a typical structure of the integrated semiconductor device of the multilayer type as the second embodiment; 
         FIG. 8  is a schematic view showing a typical test environment for the integrated semiconductor device as the second embodiment; 
         FIG. 9  is a timing chart showing typical operation timings corresponding to the chip identifiers being set of a 0th chip through a third chip in the second embodiment; and 
         FIG. 10  is a timing chart showing typical operation timings corresponding to the chip identifiers being reset of the 0th chip through the third chip in the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Some preferred embodiments of the present disclosure will now be described below. The description will be given under the following headings: 
     1. First embodiment (a structure whereby each of the chips making up a multilayer semiconductor device may be tested using signals input from a single chip selection terminal; an example in which an external control signal for designating a chip identifier to be set is input from the test device); and 
     2. Second embodiment (a structure whereby each of the chips making up a multilayer semiconductor device may be tested using signals input from a single chip selection terminal; an example in which a command for setting a chip identifier is input from the test device). 
     1. First Embodiment 
     Typical Structure of the Integrated Semiconductor Device 
       FIG. 1  schematically shows a typical structure of an integrated semiconductor device  100  as the first embodiment of the present disclosure. The integrated semiconductor device  100  includes (N+1) chips ranging from a 0th chip  200 - 0  to an Nth chip  200 -N. In  FIG. 1 , the 0th chip  200 - 0  through the Nth chip  200 -N are shown connected in multiple layers. Each of the 0th chip  200 - 0  through the Nth chip  200 -N is an individually independent semiconductor device. These chips have the same structure because they are manufactured through the same processes. In the first embodiment, each chip  200  may be assumed to be a DRAM (dynamic random access memory) in functionality but is not limited functionally thereto. 
     A typical structure of a single chip  200  is indicated by the schematic structure of the 0th chip  200 - 0  in  FIG. 1 . The chip  200  possesses the following terminals: (N+1) chip selection signal input terminals  301 A- 0  through  301 A-N, and (N+1) chip selection signal output terminals  301 B- 0  through  301 B-N. The chip selection signal input terminals  301 A- 0  through  301 A-N are paired with the chip selection signal output terminals  301 B- 0  through  301 B-N respectively, and they are interconnected internally. The chip selection signal output terminals  301 B- 0  through  301 B-N of a single chip  200 - n  are connected respectively to the chip selection signal input terminals  301 A- 0  through  301 A-N of the immediately downstream chip  200 -( n +1). 
     Each chip  200  has a control signal input terminal  302 A paired with a control signal output terminal  302 B. The control signal output terminal  302 B of a single chip  200 - n  is connected to the control signal input terminal  302 A of the immediately downstream chip  200 -( n +1). 
     Each chip  200  also has an address input terminal  303 A paired with an address output terminal  303 B. Inside the chip  200 , the address input terminal  303 A and address output terminal  303 B are interconnected. The address output terminal  303 B of a single chip  200 - n  is connected to the address input terminal  303 A of the immediately downstream chip  200 -( n +1). With this arrangement, an address signal ADR input to the 0th chip  200 - 0  at the first stage is supplied parallelly to the 0th chip  200 - 0  through the Nth chip  200 -N. 
     Each chip  200  also has a command input terminal  304 A paired with a command output terminal  304 B. Inside the chip  200 , the command input terminal  304 A and command output terminal  304 B are also interconnected. The command output terminal  304 B of a single chip  200 - n  is connected to the command input terminal  304 A of the immediately downstream chip  200 -( n +1). With this arrangement, a command signal CMD input to the 0th chip  200 - 0  at the first stage is supplied parallelly to the 0th chip  200 - 0  through the Nth chip  200 -N. 
     Each chip  200  also has a clock input terminal  305 A paired with a clock output terminal  305 B. Inside the chip  200 , the clock input terminal  305 A and clock output terminal  305 B are also interconnected. The clock output terminal  305 B of a single chip  200 - n  is connected to the clock input terminal  305 A of the immediately downstream chip  200 -( n +1). With this arrangement, a clock signal CLK input to the 0th chip  200 - 0  at the first stage is supplied parallelly to the 0th chip  200 - n  through the Nth chip  200 -N. 
     Furthermore, each chip  200  incorporates a control signal output portion  210 , a chip identifier holding portion  250 , a signal selection portion  260 , and internal circuits  290 . The control signal output portion  210  generates a downstream chip control signal TRGO upon input of an external control signal TRGI from the outside through the control signal input terminal  302 A at test time, and outputs the generated signal TRGO through the control signal output terminal  302 B. For example, the downstream chip control signal TRGO may be output in synchronism with the clock CLK. The downstream chip control signal TRGO is input to the immediately downstream chip  200  through its control signal input terminal  302 A as the external control signal TRGI. The external control signal TRGI functions as a signal for designating the chip identifier to be set on the chip  200 . The control signal output portion  210  also controls the timing at which the chip identifier holding portion  250  holds and then outputs the chip identifier using a chip identifier hold control signal REGEN and the above-mentioned downstream chip control signal TRGO for example. Incidentally, the control signal output portion  210  is an example of the control portion. 
     When the integrated semiconductor device is tested, the test device may typically input the address signal ADR to the address input terminal  303 A. The chip identifier holding portion  250  holds the value of the chip identifier indicated by the input address signal ADR designating the value of the chip identifier to be set. The chip identifier holding portion  250  holds the chip identifier value and then outputs the value as a set chip identifier HLDID. Incidentally, the chip identifier holding portion  250  is an example of the semiconductor identifier holding portion. 
     The chip identifier input as the address ADR is any one of the chip identifiers assigned to the (N+1) chips ranging from the 0th chip  200 - 0  to the Nth chip  200 -N. As a specific example, suppose that the chip identifiers (ID) to be assigned to the (N+1) chips made up of the 0th chip  200 - 0  through the Nth chip  200 -N range from “0” to “N.” In this case, one of the chip identifiers “0” through “N” is input as the address ADR. The operation timing at which to hold the chip identifier is set by the clock CLK and by the downstream chip control signal TRGO generated by the control signal output portion  210 . 
     With this embodiment, the chip selection signal input terminals  301 A- 0  through  301 A-N are provided corresponding to the chip identifiers “0” through “N,” respectively. Chip selection signals CS- 0  through CS-N are input to the chip selection signal input terminals  301 A- 0  through  301 A-N, respectively. The signal selection portion  260  selects one of the chip selection signals CS- 0  through CS-N input through the chip selection signal input terminals  301 A- 0  through  301 A-N. The signal selection portion  260  inputs as a selection control signal the set chip identifier HLDID output by the chip identifier holding portion  250 . That is, the signal selection portion  260  acts to select that chip selection signal CS-n from the chip selection signal input terminal  301 A which corresponds to the value of the chip identifier indicated by the set chip identifier HLDID. 
     The internal circuits  290  are an aggregate of the circuits that operate when the chip  200  is in normal operation. At test time, the internal circuits  290  are targeted to be tested. For example, if the chip  200  is a DRAM as mentioned above, the internal circuits  290  are composed of a memory array and its peripheral circuits. In this case, the memory array in the internal circuits  290  may be accessed in accordance with commands CMD such as a read or a write command input from the command input terminal  304 A. The access operations are timed in accordance with the clock CLK. Also, while an enabled chip selection signal CS is being input from the signal selection portion  260 , the internal circuits  290  enter an active state and become operable in response to the input command CMD. When the chip selection signal CS is not input, the internal circuits  290  are in an inactive state and reject the input of any command CMD for example. The signal selection portion  260  is an example of the signal selection portion. 
     Where the internal circuits  290  constitute a DRAM for example, suitable input/output terminals are provided in practice to handle a plurality of signals such as a clock enable signal, a row address strobe signal, a column address strobe signal, and a write enable signal. With this embodiment, for purpose of simplification and illustration, only the command input terminal  304 A and command output terminal  304 B were shown above to represent the signal terminals that may be actually configured. Although a plurality of input/output terminals are provided in practice to deal with addresses, only the address input terminal  303 A and address output terminal  303 B were shown above to represent the actual terminals that may be configured. Furthermore, the actual chip  200  possesses data input/output terminals which, however, are not shown. 
     [Typical Structure of the Integrated Semiconductor Device of the Multilayer Type] 
     The integrated semiconductor device as one embodiment of the present disclosure may be constituted in practice by chips  200  being stacked in multiple layers.  FIG. 2  shows a typical structure of the integrated semiconductor device  100  of the multilayer type. In  FIG. 2 , the 0th chip  200 - 0  is shown having a concrete structure that includes the control signal output portion  210 , chip identifier holding portion  250 , and signal selection portion  260  already indicated in  FIG. 1 .  FIG. 2  also shows a fixed chip identifier holding portion  270  for use in normal operation. For purpose of illustration, the integrated semiconductor device  100  in  FIG. 2  is shown to have only four chips ranging from the 0th chip  200 - 0  to the third chip  200 - 3 . The internal circuits  290  are not shown. 
     As illustrated in  FIG. 2 , the integrated semiconductor device  100  of the multilayer type has the 0th chip  200 - 0 , the first chip  200 - 1 , the second chip  200 - 2 , and the third chip  200 - 3  stacked from the bottom up. 
     In this structure, each chip  200  has the chip selection signal input terminals  301 A- 0  through  301 A- 3 , control signal input terminal  302 A, address input terminal  303 A, command input terminal  304 A, and clock input terminal  305 A furnished on the bottom side. Also, each chip  200  has the chip selection signal output terminals  301 B- 0  through  301 B- 3 , control signal output terminal  302 B, address output terminal  303 B, command output terminal  304 B, and clock output terminal  305 B furnished on the top side. In practice, these terminals may be formed as micro-bumps for example. 
     On each chip  200  where a given terminal (micro-bump) furnished on the top side is paired with its counterpart on the bottom side, the paired terminals are located in the same position in the plane direction. With this arrangement, between two chips  200  that are vertically stacked adjacent to each other, the terminals furnished on the top side of the lower chip are connected by contact with their paired counterparts on the bottom side of the upper chip. That is, the chip selection signal output terminals  301 B- 0  through  301 B- 3  on the top side of the lower chip  200  are connected by contact with the chip selection signal input terminals  301 A- 0  through  301 A- 3  on the bottom side of the upper chip  200 , respectively. The control signal output terminal  302 B on the top side of the lower chip  200  is connected by contact with the control signal input terminal  302 A on the bottom side of the upper chip  200 . The address output terminal  303 B on the top side of the lower chip  200  is connected by contact with the address input terminal  303 A on the bottom side of the upper chip  200 . The command output terminal  304 B on the top side of the lower chip  200  is connected by contact with the command input terminal  304 A on the bottom side of the upper chip  200 . The clock output terminal  305 B on the top side of the lower chip  200  is connected by contact with the clock input terminal  305 A on the bottom side of the upper chip  200 . 
     Inside the chip  200 , the signal lines connecting the chip selection signal input terminals  301 A- 0  through  301 A-N with the chip selection signal output terminals  301 B- 0  through  301 B-N respectively are formed as through electrodes, also known as through-silicon vias (TSV). Likewise, the signal line connecting the address input terminal  303 A with the address output terminal  303 B inside the chip  200  is formed as a through electrode. Also, the signal line connecting the command input terminal  304 A with the command output terminal  304 B and the signal line connecting the clock input terminal  305 A with the clock output terminal  305 B are formed as through electrodes. 
     Explained below are typical structures of the control signal output portion  210 , chip identifier holding portion  250 , and signal selection portion  260  shown in  FIG. 2 . The control signal output portion  210  of the first embodiment contains only an external control signal support output portion  220  inside. The external control signal support output portion  220  includes a control signal input circuit  221 , an exclusive-NOR gate  222 , an inverter  223 , and a control signal output circuit  224 . 
     The control signal input circuit  221  inputs an external control signal TRGI from the control signal input terminal  302 A and latches the input signal on the rising edge of the clock CLK for signal output. The exclusive-NOR gate  222  outputs the exclusive-NOR of the output from the control signal input circuit  221  and of the output from the inverter  223 . The output of the exclusive-NOR gate  222  is input as the chip identifier hold control signal REGEN to the enable terminal of a chip identifier register  252  in the chip identifier holding portion  250 . 
     The control signal output circuit  224  inputs the signal output by the control signal input circuit  221  and latches the input signal on the falling edge of the clock CLK for signal output. The output of the control signal output circuit  224  is output as the downstream chip control signal TRGO from the control signal output terminal  302 B. The output of the control signal output circuit  224  is also input to the inverter  223 . Furthermore, the output of the control signal output circuit  224  is input as a selector control signal to a selector  253  in the chip identifier holding portion  250 . 
     The chip identifier holding portion  250  is made up of an address input circuit  251 , the chip identifier register  252 , and the selector  253 . The address input circuit  251  inputs the signal which is fed from the address input terminal  303 A as the address ADR and which designates the chip identifier to be set, and latches the input signal on the rising edge of the clock CLK for signal output. 
     In practice, the address signal ADR may be composed of a predetermined number of bits for example. Specifically, if there are four chips  200  configured as shown in the example of  FIG. 2  so that there may be numerical chip identifiers “0” through “3,” then a minimum of two bits may be needed. The circuits making up the chip identifier holding portion  250  are structured correspondingly to address the predetermined number of bits of at least two. 
     The chip identifier register  252  holds the value of the chip identifier output by the address input circuit  251  when the chip identifier hold control signal REGEN input to the enable terminal is High, which denotes the enabled state. 
     The selector  253  selects either a register value REG output by the chip identifier register  252  or the output from the fixed chip identifier holding portion  270  in accordance with the selection control signal output by the control signal output circuit  224 , and outputs what is selected as the set chip identifier HLDID. When the selection control signal is High, the selector  253  selects the register value REG; when the selection control signal is Low, the selector  253  selects the value of a fixed identifier value output by the fixed chip identifier holding portion  270 . 
     The fixed chip identifier holding portion  270  holds a chip identifier assigned fixedly beforehand to the chip in question (i.e., fixed chip identifier). For example, the fixed chip identifier may be used for chip selection in normal operation. It is assumed here that fixed chip identifiers are assigned to the 0th chip  200 - 0  through the third chip  200 - 3  as follows: a fixed chip identifier value of “0” is assigned to the 0th chip  200 - 0 ; and fixed chip identifier values of “1,” “2” and “3” are assigned likewise to the first chip  200 - 1 , second chip  200 - 2 , and third chip  200 - 3  respectively. Incidentally, the fixed chip identifier holding portion  270  is an example of the fixed semiconductor identifier holding portion. 
     The signal selection portion  260  is composed of a single selector  260   a  as shown illustratively. For example, the selector  260   a  in  FIG. 2  may possess four input terminals connected respectively to four signal lines that in turn are connected to the chip selection signal input terminals  301 A- 0  through  301 A- 3 . When the set chip identifier HLDID input as the selection control signal is “0,” the selector  260   a  selects the signal line connected to the chip selection signal input terminal  301 A- 0 . Likewise, when the set chip identifier HLDID indicates one of the values “1” through “3,” the selector  260   a  selects the corresponding one of the signal lines connected to the chip selection signal input terminals  301 A- 0  through  301 A- 3 . The selector  260   a  proceeds to output the chip selection signal CS being output on the selected signal line to the internal circuits  290  (not shown in  FIG. 2 ). The remaining first chip  200 - 1  through third chip  200 - 3  also have the same structure as that of the 0th chip  200 - 0  shown in  FIG. 2 . 
     [Typical Test Environment for the Integrated Semiconductor Device] 
       FIG. 3  shows a typical test environment for the integrated semiconductor device  100  as the first embodiment of the present disclosure. In the example of  FIG. 3 , as in  FIG. 2 , the integrated semiconductor device  100  is shown structured with the four semiconductor chips (0th chip  200 - 0  through third chip  200 - 3 ) stacked in multiple layers. In the current context, the test means inspecting and measuring the integrated semiconductor device  100  for quality, performance, etc., at its manufacturing stage. 
     As shown in  FIG. 3 , the test environment for the integrated semiconductor device  100  is formed by first attaching a chip as a logic  400  in layered fashion to the bottom side of the 0th chip  200 - 0  at the lowest stage of the integrated semiconductor device  100 . The logic  400  controls the chips  200  of the integrated semiconductor device  100  in normal operation, and is controlled by internal circuits  420 . A package substrate  500  is attached to the bottom side of the logic  400 . As a typical product, the semiconductor integrated device  100 , logic  400 , and package substrate  500  may be integrated in a single unit. On the bottom side of the package substrate  500 , there are provided six terminals  501  through  506  corresponding to the signal lines led from a test device  600 . 
     On the top side of the logic  400 , there are provided a plurality of terminals  401  corresponding individually to the terminals disposed on the bottom side of the 0th chip  200 - 0 . That is, the terminals  401  are provided to correspond individually to the chip selection signal input terminals  301 A- 0  through  301 A-N. There are also provided terminals  401  corresponding individually to the control signal input terminal  302 A, address input terminal  303 A, command input terminal  304 A, and clock input terminal  305 A. On the top side of the logic  400  in the outer periphery of the terminals  401 , there may be provided six pads  402  through  407  for example. These six pads are connected by wire bonding to the signal lines led from the terminals  501  through  506  on the package substrate  500 . 
     The test device  600  is used to test the integrated semiconductor device  100 . The test device  600  supporting the first embodiment of the present disclosure outputs a test control signal TST, a chip selection signal CS- 0 , an external control signal TRGI- 0 , an address ADR, a command CMD, and a clock CLK with regard to a single integrated semiconductor device  100 . On the test device  600 , terminals  601  through  606  are provided to output the test control signal TST, chip selection signal CS- 0 , external control signal TRGI- 0 , address ADR, command CMD and clock CLK, respectively. In practice, groups of these signals may be output through other terminals, not shown, to a plurality of integrated semiconductor devices  100 . 
     The test control signal TST is input to the internal circuits  420  in the logic  400  via the pad  402  from the terminal  501 . The chip selection signal CS- 0  is input to one of the input terminals of a selector  411  in the logic  400  via the pad  403  from the terminal  502 . The external control signal TRGI- 0  is connected to the control signal input terminal  302 A of the 0th chip  200 - 0  via the pad  404  from the terminal  503  and via, the terminal  401  on the top side of the logic  400 . The address ADR is input to one of the input terminals of a selector  412  in the logic  400  via the pad  405  from the terminal  504 . The command CMD is input to one of the input terminals of a selector  413  via the pad  406  from the terminal  505 . The clock CLK is input to one of the input terminals of a selector  414  in the logic  400  via the pad  407  from the terminal  506 . 
     In normal operation, the internal circuits  420  of the logic  400  output one of the chip selection signals CS- 0  through CS- 3  arbitrarily. In normal operation, the internal circuits  420  may output two or more of the chip selection signals CS- 0  through CS- 3  in order to have a plurality of chips selected. The chip selection signal CS- 0  output by the internal circuits  420  is connected to the other input terminal of the selector  411 . The output of the selector  411  is fed to the chip selection signal input terminal  301 A- 0  of the 0th chip  200 - 0  via the terminal  401  corresponding to the chip selection signal CS- 0 . Also, the chip selection signals CS- 1  through CS- 3  output by the internal circuits  420  are supplied to the chip selection signal input terminals  301 A- 0  through  301 A- 3  of the first chip  200 - 0 , respectively, via the corresponding terminals  401 . 
     In normal operation, the internal circuits  420  output various addresses ADR and commands CMD as needed. The internal circuits  420  also generate and output the clock CLK. Each of the address ADR, command CMD, and clock CLK output by the internal circuits  420  is input to the other input terminal of each of the selectors  412  through  414 , respectively. The output of the selector  412  is fed to the address input terminal  303 A of the 0th chip  200 - 0  via the corresponding terminal  401 . The output of the selector  413  is sent to the address input terminal  304 A of the 0th chip  200 - 0  via the corresponding terminal  401 . The output of the selector  414  is supplied to the address input terminal  305 A of the 0th chip  200 - 0  via the corresponding terminal  401 . 
     If the test control signal TST typically goes High to indicate that test mode is in effect, the internal circuits  420  set the selectors  411  through  414  in a state that selectively outputs the signals input from the test device  600 . The settings provide the state in which the chip selection signal CS- 0 , external control signal TRGI- 0 , address ADR, command CMD, and clock CLK from the test device are input unchanged to the 0th chip  200 - 0 . That is, suitable signal paths are provided to support the test environment. 
     In normal operation, on the other hand, the test control signal TST is not input so that the signal TST may maintain Low, for example. In response, the internal circuits  420  sets the selectors  411  through  414  in a state that selectively outputs the signals output by the internal circuits  420 . The settings make it possible for the internal circuits  420  to control the chip  200  corresponding to normal operation. 
     [Outline of the Workings of the Integrated Semiconductor Device in Test Mode] 
     The following constraint exists on the testing of the integrated semiconductor device  100  as one embodiment of the present disclosure: On each of the chips  200  shown in  FIG. 2 , there are provided four chip selection signal input terminals  301 A- 0  through  301 A- 3  corresponding to the four chips  200  being stacked in layers. However, the test device is allowed to use only one terminal for connection with the chip selection signal input terminal of one integrated semiconductor device  100 . This constraint is in effect generally because of the need of one test device simultaneously to test as many integrated semiconductor devices  100  as possible. 
     Thus as shown in  FIG. 3 , the test device  600  has only one terminal  602  as the terminal through which to feed the chip selection signal to one integrated semiconductor device  100 . In this setup, only the chip selection signal CS- 0  is input from the test device  600  to each of the chips  200  constituting the integrated semiconductor device  100  via the signal path corresponding to the chip selection signal input terminal  301 A- 0 . The chip selection signal CS- 0  corresponds to the chip identifier having the value “0.” 
     In this case, for example, if a fixed chip identifier to be stored in the fixed chip identifier holding portion  270  is used in the same manner as in normal operation, only the 0th chip  200 - 0  can select the chip selection signal CS- 0  and feed it to the internal circuits  290 . That is, the 0th chip  200 - 0  alone can be tested while the remaining first chip  200 - 1  through third chip  200 - 3  remain untested. 
     With this embodiment of the present disclosure, there are provided inside the chip  200  the control signal output portion  210  and chip identifier holding portion  250  discussed above in reference to  FIG. 2 . These portions make it possible to set a desired chip identifier to each of the configured chips  200 , as will be explained below. For example, the chip identifier having the value “0” may be set to any one of the 0th chip  200 - 0  through the third chip  200 - 3 ; the remaining chips may each be assigned the chip identifier having a value other than “0.” That is, despite the condition in which only the chip selection signal CS- 0  is output from one chip selection signal input terminal  301 A- 0 , it is possible to test the 0th chip  200 - 0  through the third chip  200 - 3 . 
     [Example of the Chip Identifier Set Operation] 
     The timing chart in  FIG. 4  shows an operation example corresponding to the setting of chip identifiers performed by the integrated semiconductor device  100  of which the structure is shown in  FIG. 2 , in the test environment indicated in  FIG. 3 . 
     Where a chip identifier is to be set with the first embodiment of the disclosure in use, the chip selection signal CS- 0  and address ADR are set in a manner preventing effective signals from getting output by the test device  600 . It is assumed here that the chip selection signal CS- 0  and address ADR are Low-active signals. It follows that where the chip identifier is to be set, the chip selection signal CS- 0  and address ADR remain High when output. However, when inspection and measurement are actually performed as the tests following the setting of the chip identifier, the chip selection signal CS- 0  is output continuously and the address ADR is also output as needed. 
     Prior to time t 1  in  FIG. 4 , the test device  600  outputs a “Low” external control signal TRGI- 0  representing a disenabled state. In this condition, the control signal output circuit  224  of the control signal output portion  210  in the 0th chip  200 - 0  outputs a “Low” downstream chip control signal TRGO- 0  corresponding to the disenabled state. Also in this state, the chip identifier hold control signal REGEN input to the enable terminal of the chip identifier register  252  in the chip identifier holding portion  250  is Low reflecting the disenabled state. Thus the register value REG of the chip identifier register  252  is in the initial state where an effective chip identifier value is not held. Also in this state, with the output of the control signal output circuit  224  being “Low,” the selector  253  of the chip identifier holding portion  250  is set to select the side of the fixed chip identifier holding portion  270 . It should be noted that because the chip selection signal CS- 0  is inactive, the signal selection portion  260  does not output the effective chip selection signal CS- 0 . 
     In the above-described state, the external control signal TRGI- 0  output by the 0th chip  200 - 0  is input as an external control signal TRGI- 1  to the first chip  200 - 1  positioned immediately upward. For this reason, the first chip  200 - 1  is in the same state as the 0th chip  200 - 0 . That is, the control signal output circuit  224  outputs a “Low” downstream chip control signal TRGO- 1  corresponding to the disenabled state, and the register value REG of the chip identifier register  252  is in the initial state. Also, the downstream chip control signal TRGO- 1  is input to the second chip  200 - 2  so that a downstream chip control signal TRGO- 2  is input to the third chip  200 - 3  accordingly. Correspondingly, the register value REG of the chip identifier register  252  is in the initial state in both the second chip  200 - 2  and the third chip  200 - 3 . With the first embodiment of this disclosure, as described above, it is possible to initialize one after the other the chips making up the integrated semiconductor device  100  when the test device  600  outputs the external control signal TRGI- 0  being Low. 
     At time t 1 , the test device  600  inverts the external control signal TRGI- 0  to High corresponding to the enabled state in order to set the chip identifier, and outputs the inverted external control signal TRGI- 0 . At the same time, the test device  600  outputs the address ADR denoting the chip identifier “0” (ID=0). Incidentally, time t 1  is the point in time at which the clock CLK falls. The output of the address ADR denoting the chip identifier “0” is continued from time t 1  until time t 3  at which the clock CLK again falls following one full clock cycle from time t 1 . 
     The control signal input circuit  221  of the control signal output portion  210  in the 0th chip  200 - 0  latches the external control signal TRGI- 0  inverted to High at time t 1 , on the rising edge of the clock CLK at time t 2 . The input of the external control signal TRGI- 0  serves to instruct the 0th chip  200 - 0  to hold its chip identifier. At time t 2 , the control signal output circuit  224  maintains the “Low” output. Thus the output of the exclusive-NOR gate  222 , i.e., the chip identifier hold control signal REGEN input to the enable terminal of the chip identifier register  252 , is inverted from Low to High. 
     Meanwhile, in the chip identifier holding portion  250 , the address input circuit  251  latches the chip identifier value “0” that was output at time t 1 , at time t 2  at which the clock CLK rises, and outputs the latched chip identifier value to the chip identifier register  252 . The chip identifier register  252  holds, as the register value REG- 0 , the chip identifier value “0” being input when the input signal at the enable terminal is inverted from Low to High at the same time t 2 . The operation of holding the chip identifier value as the register value REG- 0  is continued until the external control signal TRGI- 0  is subsequently inverted to Low (disenabled), as will be discussed later. 
     At time t 3  at which the clock CLK falls, the control signal output circuit  224  of the control signal output portion  210  (external control signal support output portion  220 ) latches the output of the control signal input circuit  221  that was inverted to High at time t 2 . This causes the downstream chip control signal TRGO- 0  to be inverted from Low to High at time t 3 , and the inverted downstream chip control signal is input as the external control signal TRGI- 1  to the first chip  200 - 1  positioned immediately upward. 
     The downstream chip control signal TRGO- 0  is also input to the inverter  223 . This causes the output of the exclusive-NOR gate  222  that was inverted from Low to High at time t 2  to be again inverted to Low at time t 3 . Thereafter, the output of the exclusive-NOR gate  222  remains Low. That is, the chip identifier hold control signal REGEN is inverted from High to Low at time t 3  and remains Low thereafter. This causes the chip identifier register  252  to hold continuously the register value REG- 0  that was being held immediately before time t 3 , until the input signal to the enable terminal is subsequently inverted to High. 
     Since the downstream chip control signal TRGO- 0  serves as the selection control signal for the selector  253 , the selector  253  is set from time t 3  on to select the register value REG- 0  and to output the selected register value as the set chip identifier HLDID. In this manner, between time t 2  and time t 3 , the value of the chip identifier input as the address ADR is held as the register value REG- 0 , and the value thus held is output as the set chip identifier HLDID. This is how the chip identifier is set on the 0th chip  200 - 0 . 
     At time t 3 , the external control signal TRGI- 1  inverted to High is input to the first chip  200 - 1  as discussed above. Also at time t 3 , the test device  600  changes the signal of the address ADR denoting the chip identifier to “1” and outputs the changed signal until time t 5  following one full clock cycle of the clock CLK. As described, the workings of the first chip  200 - 1  positioned immediately upward become the same as those of the 0th chip  200 - 0  between time t 1  and time t 3 . That is, the value “1” is held at the register value REG at time t 4 , i.e., the chip identifier “1” is set. At time t 5 , the downstream chip control signal TRGO- 1  is output. 
     The above-mentioned downstream chip control signal TRGO- 1  is input to the second chip  200 - 2  as an external control signal TRGI- 2 . Between time t 5  and time t 7 , the test device  600  changes the value of the chip identifier denoted by the address ADR to, say, “2” and outputs the changed chip identifier. In this manner, the second chip  200 - 2  holds the chip identifier “2” at time t 6 . At time t 7 , the downstream chip control signal TRGO- 2  is output. 
     The downstream chip control signal TRGO- 2  is also input to the third chip  200 - 3  as an external control signal TRGI- 3 . Between time t 7  and time t 9 , the chip identifier “3” is held. At time t 9 , a downstream chip control signal TRGO- 3  is output. It should be noted that the third chip  200 - 3  is positioned highest in the stack so that the downstream chip control signal TRGO- 3  will not be input to any other chip. 
     With the first embodiment of the present disclosure, as described above, the test device  600  first inputs the enabled-state external control signal TRGI- 0  to the 0th chip  200 - 0  positioned lowest in the stack (at the first stage). The first-stage chip through the last-stage chip may then be set one after the other into the enabled state where the chip identifier can be successively input by taking advantage of one full clock cycle time difference of the clock CLK for example. In this case, the test device  600  outputs the address ADR denoting a suitable chip identifier value at intervals of the time period corresponding to one full clock cycle of the clock CLK. This makes it possible to set a suitable chip identifier to each of the chips  200  constituting the integrated semiconductor device  100 . 
     Specifically, in the example of  FIG. 4 , the test device  600  successively outputs chip identifiers “0,” “1,” “2” and “3,” in that order, during the period between time t 1  and time t 3 , the period between time t 3  and time t 5 , the period between time t 5  and time t 7 , and the period between time t 7  and time t 9 , respectively. As a result, the chip identifiers “0,” “1,” “2” and “3” are set to the first chip  200 - 0  through the third chip  200 - 3 , respectively. The value of the chip identifier output as the address ADR in each of the above-mentioned periods may be set as desired on the side of the test device  600 . Thus if the address ADR is output during each of the above periods as the chip identifiers “3,” “0,” “1” and “2,” in that order, then the 0th chip  200 - 0  through the third chip  200 - 3  are assigned the chip identifiers “3,” “0,” “1” and “2,” respectively. Likewise, if the address ADR is output during each of the above periods as the chip identifiers “2,” “3,” “0” and “1,” in that order, then the 0th chip  200 - 0  through the third chip  200 - 3  are assigned the chip identifiers “2,” “3,” “0” and “1,” respectively. In this manner, it will be appreciated that each chip may be assigned a suitable chip identifier by use of a suitable value of the chip identifier output by the test device  600  as the address ADR during each of the above-mentioned periods. 
     At actual test time, suppose for example that the chip identifiers “0,” “1,” “2” and “3” are set to the 0th chip  200 - 0  through the third chip  200 - 3 , respectively, as shown in  FIG. 4 . Thereafter, the test device  600  outputs the chip selection signal CS- 0  from the terminal  602 . The chip selection signal CS- 0  is input parallelly to the signal selection portions  260  (selectors  260   a ) of the 0th chip  200 - 0  through the third chip  200 - 3 , typically via the chip selection signal input terminal  301 A- 0  of the 0th chip  200 - 0 . At this point, only the 0th chip  200 - 0  holding the chip identifier “0” can enable the operation of the internal circuits  290  by selecting the input chip selection signal CS- 0 . That is, the 0th chip  200 - 0  is targeted for testing in this case. 
     While outputting the clock CLK for example, the test device  600  may output the command CMD, address ADR, etc., in a suitably timed manner to operate the internal circuits  290  of the 0th chip  200 - 0  for inspection and measurement. While the testing is underway, the external control signal TRGI- 0  from time t 1  on remains High corresponding to the enabled state. This perpetuates the state in which the configured chips  200  are being assigned their respective chip identifiers. 
     After the tests of the 0th chip  200 - 0  are completed, the test device  600  performs control to reset the chip identifiers that were set to the 0th chip  200 - 0  through the third chip  200 - 3  so as to bring about the initial state, as will be discussed later in reference to  FIG. 5 . 
     Through the control discussed above in reference to  FIG. 4 , the test device  600  then sets the chip identifier “0” to any one of the first chip  200 - 1  through the third chip  200 - 3  yet to be tested. At the same time, the test device  600  sets the chip identifier “1,” “2” or “3” other than “0” to the remaining three chips  200 . Then in the same manner as discussed above, the test device  600  outputs the chip selection signal CS- 0  from the terminal  602  to test the chip  200  to which the chip identifier “0” is being set. In this manner, the test device  600  sets the chip identifier “0” successively to each of the chips  200  making up the integrated semiconductor device  100  in order to test each of the chips individually. 
     As a specific example, this embodiment may set the chip identifier to each of the 0th chip  200 - 0  through the third chip  200 - 3  in the following steps: First, the chip identifiers “0,” “1,” “2” and “3” are set to the 0th chip  200 - 0  through the third chip  200 - 3 , respectively, to test the 0th chip  200 - 0  as described above. Next, the chip identifiers “3,” “0,” “1” and “2” are set to the 0th chip  200 - 0  through the third chip  200 - 3 , respectively, to test the first chip  200 - 1 . Then the chip identifiers “2,” “3,” “0” and “1” are set to the 0th chip  200 - 0  through the third chip  200 - 3 , respectively, to test the second chip  200 - 2 . Finally, the chip identifiers “1,” “2,” “3” and “0” are set to the 0th chip  200 - 0  through the third chip  200 - 3 , respectively, to test the third chip  200 - 3 . 
     However, as will be understood from the foregoing explanation, the chip identifier “0” need only be set to the chip  200  that is targeted for testing with this embodiment of the present disclosure. The other chips  200  not targeted to be tested may each be assigned any chip identifier value other than “0.” In addition, the chip identifiers set to the other chips not targeted for testing may overlap with one another with no problem. Therefore, the chip identifier “0” may be set only to the chip  200  targeted for testing and the chip identifier “1” may be set to all other chips  200  for example. In any case, this embodiment of the disclosure allows a desired chip identifier to be set to each of the chips  200  configured. 
     [Example of the Chip Identifier Reset Operation] 
     The timing chart in  FIG. 5  shows an example of the operation performed by the integrated semiconductor device  100  of which the structure is shown in  FIG. 2 , when the chip identifiers set on the configured chips  200  typically by the operation indicated in  FIG. 4  are to be reset (i.e. initialized). This operation may be carried out typically in order to reset the chip identifiers held by the chips  200  when the chip identifier “0” is to be set on a chip  200  yet to be tested. 
     As the precondition for performing the operation to reset the chip identifiers, the test device  600  does not output the chip selection signal CS- 0  and command CMD. This precondition is the same as that for setting the chip identifiers shown in  FIG. 4 . In addition, the address ADR is not output when the chip identifiers are to be reset. That is, no signal is output to designate the chip identifier to be set. 
     In  FIG. 5 , the period prior to time t 10  represents the state where the 0th chip  200 - 0  through the third chip  200 - 3  hold their respective chip identifiers “0,” “1,” “2” and “3” subsequent to time t 9  in  FIG. 4 , for example. In order to reset the chip identifiers being held, the test device  600  inverts the external control signal TRGI- 0  from High (enable) to Low and maintains this status thereafter. In  FIG. 5 , the external control signal TRGI- 0  is shown inverted from High to Low at time t 10  at which the clock CLK falls. 
     When the external control signal TRGI- 0  inverted to Low is input to the 0th chip  200 - 0  at time t 10 , the control signal input circuit  221  of the control signal output portion  210  (external control signal support output portion  220 ) in  FIG. 2  operates as follows: At time t 11  at which the clock CLK rises a half clock cycle after time t 10 , the control signal input circuit  221  latches the above-mentioned external control signal TRGI- 0  being Low and outputs the latched signal. This inverts the output of the control signal input circuit  221  from High to Low at time t 11 . In turn, at time t 12  at which the clock CLK falls a half clock cycle after time t 11 , the control signal output circuit  224  latches the “Low” output of the control signal input circuit  221  and outputs the latched signal. As a result, at time t 12  following one full clock cycle from time t 11  at which the external control signal TRGI- 0  was inverted to Low, the downstream chip control signal TRGO- 0  (external control signal TRGI- 1 ) is inverted from High to Low. 
     In keeping with the operation above, the inputs to the exclusive-NOR gate  222  go Low each during the period between time t 11  and time t 12 , so that the chip identifier hold control signal REGEN is brought High. This puts the chip identifier register  252  of the chip identifier holding portion  250  in the enabled state. As mentioned above, no effective address ADR is input at reset time. Thus between time t 11  and time t 12 , no effective chip identifier value is input to the chip identifier register  252 . This means that from time t 11  on, the register value REG remains the value corresponding to the initial state. At time t 12 , the downstream chip control signal TRGO- 0  is brought Low as described above. In turn, the selector  253  of the chip identifier holding portion  250  is set to select the fixed chip identifier from the fixed chip identifier holding portion  270  so that the selected identifier may be output as the set chip identifier HLDID. In this manner, between time t 11  and time t 12 , the register value REG- 0  in the chip identifier holding portion  250  is set to the initial state, and the register value REG- 0  of the initial state is not output as the set chip identifier HLDID. That is, a state is brought about in which the chip identifier set earlier by the chip identifier set operation is reset. 
     Next, the downstream chip control signal TRGO- 0  inverted to Low at time t 12  is output by the 0th chip  200 - 0  and input to the first chip  200 - 1  as the external control signal TRGI- 1 . This causes the first chip  200 - 1  to perform the same operation discussed above, thereby initializing at time t 13  the register value REG that is the output of the chip identifier register  252  and outputting at time t 14  the downstream chip control signal TRGO- 1  inverted to Low. Upon input of the downstream chip control signal TRGO- 1  as the external control signal TRGI- 2 , the second chip  200 - 2  initializes at time t 15  the register value REG that is the output of the chip identifier register  252 . At time t 16 , the second chip  200 - 2  outputs the downstream chip control signal TRGO- 2  inverted to Low. Also, upon input of the downstream chip control signal TRGO- 2  as the external control signal TRGI- 3 , the third chip  200 - 3  initializes at time t 17  the register value REG that is the output of the chip identifier register  252 . At time t 18 , the third chip  200 - 3  outputs the downstream chip control signal TRGO- 3  inverted to Low. 
     At reset time, as discussed above, the external control signal TRGI- 0  output by the test device  600  is inverted from High to Low. This allows the chips  200  making up the integrated semiconductor device  100  to reset their chip identifiers one after the other at intervals of one full clock cycle of the clock CLK starting at the lowest chip (the least downstream chip) and ending at the highest chip (the most downstream chip). 
     The exclusive-NOR gate  222  furnished in the external control signal support output portion  220  shown in  FIG. 2  may be replaced by an AND gate for example. In this case, upon resetting of the chip identifier, the enable signal is not input from the exclusive-NOR gate  222 , so that the chip identifier register  252  continuously holds the register value REG in effect since before time t 10 . That is, the chip identifier is not initialized in the chip identifier register  252  itself. However, in the case of the 0th chip  200 - 0  for example, the downstream chip control signal TRGO goes Low at time t 12 , so that the selector  253  is set also to select the fixed identifier of the fixed chip identifier holding portion  270 . Where the fixed identifier is thus selected by the selector  253  at time t 12 , the register value REG is not output as the set chip identifier HLDID, so that the initial state is actually in effect. Therefore there is little problem with the operation even though the chip identifier register  252  continuously holds the register value REG since before time t 10 . This operation also holds for the second embodiment of this disclosure, to be explained below. 
     According to the first embodiment of this disclosure, as described above, the test device  600  first outputs the external control signal TRGI- 0  to the 0th chip  200 - 0  at the first stage. In turn, the 0th chip  200 - 0  (first stage) through the Nth chip  200 -N (last stage) are assigned, one after the other in that order, a time period in which the chip identifier can be set, at intervals of one full clock cycle of the clock CLK. In keeping with each time period in which the chip identifier can be set, the test device  600  outputs the signal of the address ADR denoting the chip identifier to be set. As a result, the chip identifier is set at intervals of one full clock cycle of the clock CLK to each of the 0th chip  200 - 0  (first stage) to the Nth chip  200 -N (last stage), in that order. In this manner, even where the test device  600  is in a state of outputting only one chip selection signal, the identifier to be set on each chip may be changed as desired so that all chips constituting the integrated semiconductor device  100  can be tested. Correspondingly, the number of the terminals to be assigned by the test device  600  to one integrated semiconductor device  100  is reduced. This makes it possible, for example, to test simultaneously more integrated semiconductor devices  100  than before, thereby contributing to more efficient volume production of the integrated semiconductor devices  100 . 
     2. Second Embodiment 
     Typical Structure of the Integrated Semiconductor Device 
       FIG. 6  shows a typical structure of an integrated semiconductor device  100  as the second embodiment of the present disclosure. Of the reference numerals in  FIG. 6 , those already used in  FIG. 1  designate like or corresponding parts, and their descriptions will be omitted hereunder. For example, each of the chips  200  shown in  FIG. 6  has the same terminals as those indicated in  FIG. 1 . In addition to these terminals, each chip  200  is provided with a reset signal output terminal  306 A paired with a reset signal input terminal  306 B. An input reset signal RSTI input through the reset signal input terminal  306 B is input to the control signal output portion  210 . The control signal output portion  210  outputs an output reset signal RSTO to the reset signal output terminal  306 A. 
     Also, the control signal output portion  210  of the second embodiment inputs the command CMD fed from the address input terminal  304 A. 
     [Typical Structure of the Integrated Semiconductor Device of the Multilayer Type] 
       FIG. 7  shows a typical structure of the integrated semiconductor device  100  as the multilayer type of the second embodiment indicated in  FIG. 6 . In the case of the multilayer type, the above-mentioned reset signal output terminal  306 A and reset signal input terminal  306 B may be formed typically as micro-bumps and positioned on the bottom side and top side, respectively, of the chip  200 . The reset signal output terminal  306 A and reset signal input terminal  306 B are located in the same position in the plane direction of the chip  200 . With this arrangement, as with the other terminals, the reset signal input terminal  306 B on the top side of the lower chip is connected by contact with the reset signal output terminal  306 A on the bottom side of the upper chip  200 . 
     As shown for the 0th chip  200 - 0  in  FIG. 7 , the control signal output portion  210  of the second embodiment is furnished with a command support output portion  240  in addition to the external control signal support output portion  220  included in  FIG. 1 . Also, a selector  230  is added to the external control signal support output portion  220 . 
     The command support output portion  240  generates a signal TRGCM from which to originate the downstream chip control signal TRGO in response to the input of a command (chip identifier set command) ID_SET (one of the commands CMD) for designating the chip identifier to be set. The command support output portion  240  includes a command decoder  241 , an OR gate  242 , a command pulse latch circuit  243 , an inverter  244 , an AND gate  245 , an inverter  246 , and a control signal register  247 . 
     The command decoder  241  outputs a pulse signal (command pulse) in response to the input of the above-mentioned chip identifier set command ID_SET. In practice, the command decoder  241  is included in the internal circuits  290 , not shown. Originally, the command decoder  241  is provided to interpret various commands CMD and thereby to control the parts constituting the internal circuits  290 . For this reason, the command decoder  241  is designed to operate only when the chip selection signal CS is being input. 
     The OR gate  242  outputs the OR of the input reset signal RSTI input from the reset signal input terminal  306 B and of the command pulse output by the command decoder  241 . The output terminal of the OR gate  242  is connected to the input terminal of the command pulse latch circuit  243  and to one input terminal of the AND gate  245 . The output terminal of the OR gate  242  is also connected to the reset signal output terminal  306 A. 
     The command pulse latch circuit  243  latches the input command pulse on the rising edge of the clock CLK. The AND gate  245  outputs the AND of the output from the command pulse latch circuit  243  and of the output from the command pulse latch circuit  243  inverted by the inverter  244 . 
     Depending on the status of an enable signal, the control signal register  247  latches and holds the downstream chip control signal TRGO inverted by the inverter  246 . The enable signal to the control signal register  247  is the output from the AND gate  245 . The output of the control signal register  247  serves as the command support control signal TRGCM. 
     When a “High” command support control signal TRGCM corresponding to the enabled state is obtained from the control signal register  247 , the selector  230  selects and outputs the signal TRGCM from the control signal register  247 . If the latch output from the control signal input circuit  221  is High corresponding to the enabled state, then the selector  230  selectively outputs the latch output from the control signal input circuit  221 . The command support control signal TRGCM from the control signal register  247  and the latch output from the control signal input circuit  221  are not output simultaneously. However, even if the two signals are output simultaneously, there is little problem with the operation. For this reason, the selector  230  may be composed of a single OR gate  230   a  as shown illustratively. It should be noted that the output of the selector  230  is fed to one input terminal of the exclusive-NOR gate  222  and to the input terminal of the control signal output circuit  224 . 
     As will be understood from the ensuing explanation, the command support output portion  240  operates effectively only in the 0th chip  200 - 0  at the first stage upon chip identifier setting at test time. From the second stage onward, each of the first chip  200 - 1  through the third chip  200 - 3  has its chip identifier set by operation of the external control signal support output portion  220  as in the case of the first embodiment. However, since all chips  200  are manufactured through the same processes, the first chip  200 - 1  through the third chip  200 - 3  of the second embodiment possess a circuit structure that includes the command support output portion  240  as with the 0th chip  200 - 0  shown in  FIG. 7 . 
     [Typical Test Environment for the Integrated Semiconductor Device] 
       FIG. 8  shows a typical test environment for the integrated semiconductor device  100  as the second embodiment of the present disclosure. Of the reference numerals in  FIG. 8 , those already used in  FIG. 3  corresponding to the first embodiment designate like or corresponding parts, and their descriptions will be omitted hereunder. 
     In the test environment of  FIG. 8 , there is no terminal  603  that is furnished on the test device  600  in  FIG. 3 , the terminal being used to output the external control signal TRGI- 0 . That is, with the second embodiment, the test device  600  does not output the external control signal TRGI- 0  as a trigger to set the chip identifier to the chip  200 . The test device  600  of the second embodiment thus has one less terminal to be assigned to one integrated semiconductor device  100  than the first embodiment. Correspondingly, no signal line is connected to the pad  404  of the logic  400 . Also, the terminal  401  corresponding to the control signal input terminal  302 A of the 0th chip  200 - 0  on the top side of the logic  400  is not connected and therefore left open. 
     The reset signal RSTI (RSTO) is used solely on the side of the chips  200  making up the integrated semiconductor device  100  and need not be input to the logic  400 . For this reason, the terminal  401  corresponding to the reset signal output terminal  306 A of the logic  400  is not connected to any signal line and thus left open. In practice, however, some signal line may be connected to the terminal  401 . 
     [Example of the Chip Identifier Set Operation] 
     The timing chart in  FIG. 9  shows an operation example corresponding to the setting of chip identifiers performed by the integrated semiconductor device  100  of which the structure is shown in  FIG. 7 , in the test environment indicated in  FIG. 8 . During the chip identifier setting operation performed by the first embodiment explained above in reference to  FIG. 3 , the chip selection signal CS- 0  and command CMD are not output. By contrast, with the second embodiment operating as shown in  FIG. 9 , the chip selection signal CS- 0  and command CMD (chip identifier set command ID_SET) are output using the timings to be explained below. The address ADR is output in order of the chip identifiers “0,” “1,” “2” and “3” using the same timings as those of the first embodiment shown in  FIG. 4 . 
     Prior to time t 1  in  FIG. 9 , the chip identifier register  252  of each chip  200  is in the initial state not holding an effective chip identifier. In the initial state, the control signal output circuit  224  and control signal register  247  of the control signal output portion  210  give a “low” output corresponding to the disenabled state. At this point, the selector  253  of each chip  200  selects the fixed chip identifier held in the fixed chip identifier holding portion  270  and outputs the selected identifier as the selection control signal of the signal selection portion  260  (selector  260   a ). It is assumed here that fixed chip identifiers “0,” “1,” “2” and “3” are assigned to the 0th chip  200 - 0  through the third chip  200 - 3 , respectively. 
     In order to set the chip identifier with the second embodiment, the test device  600  outputs the chip identifier set command ID_SET from the terminal  605  corresponding to the command CMD. The output timing here is one full clock cycle between time t 1  at which the clock CLK falls and time t 3  at which the clock CLK again falls, as shown in  FIG. 9 . During the same time period between time t 1  and time t 3 , the test device  600  outputs the chip selection signal CS- 0  from the terminal  602 . Also between time t 1  and time t 3 , the test device  600  outputs the address signal ADR denoting the chip identifier “0” from the terminal  604 . The chip identifier set command ID_SET output by the test device  600  to set the chip identifier is an example of the hold command. 
     The chip selection signal CS- 0  is input to the 0th chip  200 - 0  through the third chip  200 - 3  initially during the time period between time t 1  and time t 3 . At this point, the chip selection signal CS- 0  corresponds to the chip identifier “0.” In this case, only in the 0th chip  200 - 0  at the first stage among the 0th chip  200 - 0  through the third chip  200 - 3  can the signal selection portion  260  select the chip selection signal CS- 0  and feed the selected signal to the internal circuits  290 . Thus during the time period between time t 1  and time t 3 , the command decoder  241  may operate in response to the command CMD only in the 0th chip  200 - 0  among the 0th chip  200 - 0  through the third chip  200 - 3 . 
     As described, the command decoder  241  of only the 0th chip  200 - 0  works to output a “High” command pulse between time t 1  and time t 3  in response to the chip identifier set command ID_SET being input during the same time period between t 1  and time t 3 . 
     In the command support output portion  240  of the 0th chip  200 - 0 , the above-mentioned “High” command pulse is input to the AND gate  245  via the OR gate  242 . Since the output of the command pulse latch circuit  243  is still Low at time t 1 , the inverter  244  maintains the “High” output. Thus when the “High” command pulse is input at time t 1 , the output of the AND gate  245  is inverted from Low to High. At time t 2  at which the clock CLK rises, the command pulse latch circuit  243  latches the “high” command pulse. In turn, the AND gate  245  gives a “Low” output at time t 2 . That is, the AND gate  245  goes High between time t 1  and time t 2 . 
     A “High” enable signal is input to the control signal register  247  during the time period between time t 1  and time t 2 . The external control signal TRGI- 1  output by the control signal output circuit  224  maintains the “Low” state up to time t 3 , as will be discussed later. Accordingly, between time t 1  and time t 2 , the control signal output circuit  224  latches the external control signal TRGI- 1  fed to the input terminal and inverted to High. From time t 2  on when the enable signal is brought Low, the control signal output circuit  224  continuously outputs the latched “High” signal. That is, as shown in  FIG. 9 , the “High” command support control signal TRGCM is output from time t 1  onward. 
     The above-mentioned “High” command support control signal TRGCM is output through the OR gate  230   a  of the selector  230 . In turn, the control signal output circuit  224  of the external control signal support output portion  220  latches the “High” command support control signal TRGCM at time t 3  at which the clock CLK falls. This allows the “High” downstream chip control signal TRGO- 0  to be output from time t 3  on. 
     Also from time t 1  on, when the “High” command support control signal TRGCM is input to the OR gate  230   a , the input of the “High” command support control signal TRGCM puts the chip identifier hold control signal REGEN in the enabled state. In this state, the chip identifier register  252  inputs and holds the signal which is latched by the address input circuit  251  at time t 2  and which denotes the chip identifier “0.” Then from time t 2  on, the chip identifier register  252  continuously outputs the register value REG typically denoting the chip identifier “0.” At time t 3 , with the downstream chip control signal TRGO- 0  inverted to High, the selector  253  in the chip identifier holding portion  250  outputs the register value REG of the chip identifier register  252  as the set chip identifier HLDID. Thus in the timeline up to time t 3 , the chip identifier “0” is set to the 0th chip  200 - 0 . 
     Also, the “High” downstream chip control signal TRGO- 0  output by the 0th chip  200 - 0  at time t 3  is input as the external control signal TRGI- 1  to the first chip  200 - 1  positioned immediately upward. In turn, the first chip  200 - 1  operates in the same manner as with the first embodiment. As a result, as shown in  FIG. 9 , the first chip  200 - 1  holds the register value REG indicative of the chip identifier “1” from time t 4  on, a half clock cycle of the clock CLK after time t 3 . From time t 5  on, one full clock cycle of the clock CLK after time t 3 , the first chip  200 - 1  outputs the downstream chip control signal TRGO- 1  (TRGI- 2 ). From time t 6  onward, the second chip  200 - 2  holds the register value REG indicative of the chip identifier “2.” From time t 7  on, the second chip  200 - 2  outputs the downstream chip control signal TRGO- 2  (TRGI- 3 ). From time t 8  onward, the third chip  200 - 3  holds the register value REG indicative of the chip identifier “3.” From time t 9  on, the third chip  200 - 3  outputs the downstream chip control signal TRGO- 3 . 
     [Example of the Chip Identifier Reset Operation] 
     The timing chart in  FIG. 10  shows an example of the operation performed by the integrated semiconductor device  100  of which the structure is shown in  FIG. 7 , when chip identifiers are to be reset (i.e. initialized). Prior to time t 10  in  FIG. 10  is the state in which each of the 0th chip  200 - 0  through the third chip  200 - 3  has its chip identifier being set thereto. 
     In order to reset the chip identifier with the second embodiment, the test device  600  outputs the chip selection signal CS- 0  and chip identifier set command ID_SET between time t 10  and time t 12  as shown in  FIG. 10 . Where any chip identifier is already set, the chip identifier set command ID_SET serves to designate the chip identifier to be reset. The chip identifier set command ID_SET output by the test device  600  to reset the chip identifier is an example of the initialization command, described in the appended claims. 
     At this point, one of the 0th chip  200 - 0  through the third chip  200 - 3  has the chip identifier “0” set thereto. It is assumed here for example that the chip identifier “0” is set to the third chip  200 - 3  at the highest stage. In this case, only the command decoder  241  of the third chip  200 - 3  outputs the command pulse in response to the chip identifier set command ID_SET. The command pulse is fed to the reset signal output terminal  306 A as an output reset signal RSTO- 3  via the OR gate  242 . The reset signal output terminal  306 A of the third chip  200 - 3  is connected to the reset signal input terminal  306 B of the second chip  200 - 2 . This allows the output reset signal RSTO- 3  to be input to the second chip  200 - 2  as an input reset signal RSTI- 2 . Also, the input reset signal RSTI- 2  is output as an output reset signal RSTO- 2  that is input to the first chip  200 - 1  as an input reset signal RSTI- 1 . Furthermore, the input reset signal RSTI- 1  is output by the first chip  200 - 1  as an output reset signal RSTO- 1  that is input to the 0th chip  200 - 0  as an input reset signal RSTI- 0 . 
     As described above, the reset signal is forwarded successively through the layered chips  200  from one to the other starting at the highest-positioned chip and ending at the lowest-positioned chip. Thus the “High” reset signal is input to the 0th chip  200 - 0  between time t 10  and time t 12 . 
     At time t 10 , the control signal register  247  of the command support output portion  240  in the 0th chip  200 - 0  is in the state of outputting the command support control signal TRGCM being High. In this state, the input of a “High” reset signal to the command pulse latch circuit  243  causes the AND gate  245  to go High between time t 10  and time t 12 . Because the downstream chip control signal TRGO- 0  is High between time t 10  and t 12 , the control signal register  247  latches Low. 
     During the above-described operation, both inputs to the exclusive-NOR gate  222  of the external control signal support output portion  220  are Low, so that between time t 10  and time t 12 , the chip identifier hold control signal REGEN goes High corresponding to the enabled state. At time t 11  at which the clock CLK rises (between time t 10  and time  12 ), the chip identifier holding portion  250  inputs the address ADR latched by the address input circuit  251 . However, since no effective address ADR is input at reset time, the register value REG of the chip identifier register  252  is initialized from time t 11  on. 
     The “Low” command support control signal TRGCM output from time t 10  on is latched by the control signal output circuit  224  of the external control signal support output portion  220  at time t 12  at which the clock CLK falls. Thus from time t 12  on, the downstream chip control signal TRGO- 0  is Low when output. Correspondingly, from time t 12  onward, the selector  253  is set to select the fixed chip identifier from the fixed chip identifier holding portion  270  and to output the selected identifier as the set chip identifier HLDID. In this manner, the operation up to time t 12  brings about the state in which the chip identifier having been set to the 0th chip  200 - 0  so far is reset. 
     From time  12  on, with the “Low” downstream chip control signal TRGO- 0  output as described above, the same operation as that discussed earlier in reference to  FIG. 5  is carried out by the remaining first chip  200 - 1  through third chip  200 - 3 . That is, when the external control signal TRGI input successively to each of the first chip  200 - 1  through the third chip  200 - 3  goes Low, the register value REG of the chip identifier register  252  in the applicable chip is initialized. Each chip  200  inverts the downstream chip control signal TRGO to Low before outputting the inverted signal TRGO to the chip  200  positioned immediately upward. In this manner, with the second embodiment, the input of the chip identifier set command ID_SET is used as a trigger to initialize successively each of the chip identifiers set on the 0th chip  200 - 0  through the third chip  200 - 3 . 
     With the second embodiment of the present disclosure in use, the test device  600  is caused to output as a command CMD the chip identifier set command ID_SET designating the chip identifier to be set or reset (i.e., initialized) as described above. In response to the chip identifier set command ID_SET being input, each of the chips  200  constituting the integrated semiconductor device  100  has its chip identifier set or reset successively at intervals of one full clock cycle of the clock CLK, starting at the lowest-positioned chip and ending at the highest-positioned chip. Thus the second embodiment makes it possible for the test device  600  to reduce the number of its terminals for outputting the external control signal TRGI to the integrated semiconductor device  100 . 
     In the above-described embodiments of the present disclosure, the logical circuit structures of the control signal output portion  210 , chip identifier holding portion  250 , etc., illustrated specifically in  FIGS. 2 and 7  are only examples. Other suitable structures may be adopted instead as long as the workings similar to those discussed above are ensured thereby. 
     The setting of the chip identifier was shown carried out at test time in conjunction with the above-described embodiments. Alternatively, the chip identifier set operation may be likewise performed typically under control of the logic in normal operation as well. 
     The embodiments and their variations described above are merely examples in which the present disclosure may be implemented. As is clear from above, the particulars of the embodiments and their variations in the description of the preferred embodiments correspond basically to the disclosed matters. Likewise, the disclosed matters correspond basically to the particulars with the same names in the description of the preferred embodiments. However, these embodiments and their variations and other examples of the present disclosure are not limitative thereof, and it should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factor in so far as they are within the scope of the invention. 
     The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2010-131346 filed in the Japan Patent Office on Jun. 8, 2010, the entire content of which is hereby incorporated by reference.