# Patent

## Title
Apparatus and method for testing for defects between memory cells in

## Abstract

This application is a division of application Ser. No. 08/294,127, filed on Aug. 22, 1994.

## Background
1. Reference to Appendix

Appendix A is a part of the present disclosure, and is incorporated herein by reference in its entirety.

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.

2. Field of the Invention

The present invention is related generally to monitoring operation of an integrated circuit and in particular to an integrated circuit output port for transporting information concerning any user selected operation of the integrated circuit from the integrated circuit.

3. Description of Related Art

As the form factor of hard disk drives become smaller and as the level integration for all disk drives becomes greater, the number of functions performed by a single integrated circuit in a disk drive increases substantially. As the number of functions performed by an integrated circuit increases, i.e., as the integration level increases, many of the functions are performed completely internally to the integrated circuit.

For functions that are performed completely internally, neither input, output, nor intermediate signals are available at pins of the integrated circuit. Further, the integrated circuit package size limits the number of available pins. The limited number of pins makes it unfeasible to route representative signals for each of the internal functions to a pin. Consequently, monitoring and testing of highly integrated circuits becomes problematic.

In the area of disk drive controllers, integration is becoming increasingly greater. Disk drive controller circuits that previously occupied a plug-in board are now packaged in a single integrated circuit. The plug-in boards had space for test points, switches for generating test signals, and other commonly known features that permitted relatively easy verification of the operation of the disk controller. When the same functionality is provided in an integrated circuit, there is no space for test points, switches and similar circuitry.

Therefore, typically, computer simulations are used to verify the operation of circuitry that is totally internal to an integrated circuit. Unfortunately, such simulations do not provide reliable information on the actual application performance of the integrated circuit. To obtain reliable application performance data, a way is needed to obtain information concerning all of the circuits within the integrated circuit while the circuits are in operation.

In accordance with the principles of this invention, a two-wire dedicated diagnostic data port is included in an integrated circuit such as a mixed signal CMOS large scale integrated circuit. In another embodiment, the two-wire dedicated diagnostic data port is included in a very large scale integrated circuit. The dedicated diagnostic data port provides visibility for all internal functions of an integrated circuit. Herein, an internal function, e.g., an internal signal, is a signal that is not provided directly to a pin of the integrated circuit, or is not observable through an intermediate signal that is provided to a pin of the integrated circuit. Therefore, the need to provide additional circuitry onboard the integrated circuit for each internal signal or function that must be monitored has been eliminated.

Specifically, the dedicated diagnostic data port of this invention is a programmable data port that can be used in development and testing processes related to operation of the integrated circuit as well as monitoring normal functioning of the integrated circuit. The dedicated diagnostic data port is available at all times and does not inhibit any functions of the integrated circuit during its operation.

An internal signal or signals are written to a serially connected memory in the dedicated diagnostic data port. The serially connected memory is connected to a two-wire output port of the dedicated diagnostic data port which in this embodiment is two pins of the integrated circuit. A first wire in the two-wire output port is a data wire and a second wire in the two-wire output port is a clock wire.

Transfer of the stored information from the serially connected memory to the two-wire output port is initiated by writing to a control register in the dedicated diagnostic data port. In response to writing to the control register, a clock signal on a clock input line to the dedicated diagnostic data port is coupled to the second wire, and is used to serially shift the stored information from the serially connected memory to the data wire. In one embodiment, the serially connected memory is a plurality of serially connected registers that are connected to a processor data bus and coupled to a processor address bus so that the processor can load data, i.e., internal signals, into the serially connected memory.

The signals on the two-wires from the integrated circuit are processed by a shift/latch control circuit that is external to the integrated circuit. A predetermined time after the clock signal on the clock wire terminates, i.e., remains inactive for a predetermined period, the shift/latch control circuit generates a latch signal that can be used to capture the data transmitted over the data wire.

The shift/latch control circuit eliminates the need for a three wire synchronous interface. Specifically, according to the principles of this invention, a latch signal is generated by detecting that the clock sequence has stopped after the clock sequence was started. Typically, in a three wire synchronous interface, the third wire carries a shift enable versus a latch signal. However, with the shift/latch control circuit, only the two-wires are required. This is a significant improvement, because it reduces the number of pins of an integrated circuit that are needed to support the dedicated diagnostic data port of this invention. As is known to those skilled in the art, as the integration on a chip increases, one of the limiting factors is the number of pins on the integrated circuit.

In one embodiment, the shift/latch control circuit includes an oscillator circuit that generates a second clock signal having a second frequency that is less than the clock frequency, i.e., the first clock frequency, on the clock wire of the dedicated diagnostic data port. A first storage element in the shift/latch control circuit has a clock terminal that is coupled to the oscillator circuit; an input terminal that is connected to an active signal source; and a clear terminal that is coupled to the clock wire of the dedicated diagnostic data port. Thus, when the first clock signal is active, the first storage element is normally cleared before the second clock signal can load the active signal into the first storage element. However, the timing of the first and second clock signals may be such that the active signal is loaded in the first storage element and applied to an input terminal of a second storage element.

The second storage element in the shift/latch control circuit also has a clock terminal that is coupled to the oscillator circuit, and a clear terminal that is coupled to the clock wire of the dedicated diagnostic data port. Thus, the first and second storage elements are cleared by the first clock signal on the dedicated diagnostic data port clock wire before the active signal in the first storage element can be loaded into the second storage element by the second clock signal from the oscillator circuit.

However, when the first clock signal remains inactive, i.e., in a predetermined state, for a predetermined time period, the active signal is clocked by the second clock signal through the first and second storage elements to an output terminal of the second storage element.

The output terminal of the second storage element is connected to a clock terminal of a third storage element in the shift/latch control circuit. An input terminal of the third storage element is connected to an active signal source and so the rising edge on the clock terminal from the second storage element drives the signal on its output terminal active which in turn is a latch signal that has been generated a predetermined time interval after termination of the first clock signal on the clock wire.

FIG. 1 is a block diagram of an integrated circuit containing the diagnostic data port of this invention.

FIG. 2 is a block diagram of the diagnostic data port of this invention.

FIG. 3 is a block diagram of one embodiment of a diagnostic interface board of this invention.

FIG. 4 is a schematic diagram of one embodiment of the shift/latch control circuit on the diagnostic interface board of this invention.

FIG. 5 is a schematic of one embodiment of the translation amplifier circuit on the diagnostic interface board of this invention.

FIG. 6 is a more detailed diagram of the diagnostic data port of this invention.

In accordance with the principles of this invention, a dedicated diagnostic data port 100 is included in a mixed signal CMOS large scale integrated motion control integrated circuit 150 for a disk drive. Dedicated diagnostic data port 100 provides visibility for all internal functions of integrated circuit 150. Specifically, dedicated diagnostic data port 100 of this invention is a programmable data port that can be used in development and testing processes. Dedicated diagnostic data port 100 is available at all times and does not inhibit any functions of integrated circuit 150 during its operation.

In one embodiment, diagnostic data port 100 of this invention is included in an integrated circuit 150 that includes in addition to diagnostic data port 100: a digital signal processor (DSP) system 110 that includes a DSP core, random access memory (RAM), read-only memory (ROM), timers, and an interrupt controller; a RS-232 serial port 111; a host interface port 112; a programmable servo burst decoder circuit 113 that includes a synchronization detector and gray code decoder 115 and a demodulator and timing control circuit 114; an analog data acquisition circuit 116; a position VCM control circuit 117; a spindle control circuit 118; and a power management circuit 119. The particular configuration of the circuits included within integrated circuit 150 that contains diagnostic data port 100 are not critical to this invention. Herein, DSP system 110 is sometimes referred to as DSP 110.

One embodiment of programmable servo burst decoder 113 suitable for use in this invention is described in copending, commonly filed, and commonly assigned, U.S. patent application Ser. No. 08/293,981, entitled "A Programmable Servo Burst Decoder" of Nicolas C. Assouad et al. filed on Aug. 22, 1994, which is incorporated herein by reference in its entirety. Programmable servo burst decoder 113 includes a programmable timing mark sequencer and a programmable burst sequencer as described more completely in U.S. patent application Ser. No. 08/293,981, entitled "A Programmable Servo Burst Decoder." One embodiment of an analog data acquisition system 116 suitable for use in this invention is described in copending, commonly filed, and commonly assigned, U.S. patent application Ser. No. 08/293,973, entitled "Analog Data Acquisition System For Servo Position Bursts," of John P. Hill, filed on Aug. 22, 1994 which is incorporated herein by reference in its entirety.

In this embodiment, diagnostic data port 100 sits on an address and data bus 120 of DSP 110. Consequently, any data available to DSP 110 can be supplied to diagnostic data port 100. Therefore, a wide variety of internal data of integrated circuit 150 can be sent off chip by DSP 110 writing the internal data to diagnostic data port 100.

A more detailed block diagram of diagnostic data port 100 is presented in FIG. 2. In this embodiment, diagnostic data port 100 includes a serially connected memory 230, a control register 231, and a two-wire unidirectional serial interface 240. Serially connected memory 230, in this embodiment, includes three serially linked 16-bit registers 232, 234 and 236, that are individually both readable and writable by DSP 110 using DSP data bus and DSP address bus 120. The serial output terminal of register 236 is connected to diagnostic data out pin DDO of integrated circuit 150, that is a first output terminal of diagnostic data port 100.

A second output terminal of diagnostic data port 100 is diagnostic clock out pin DCO. The clock signal on diagnostic clock out pin DCO is a diagnostic clock signal driven by the clock signal on line BCLOCK2 that serially shifts data through register 232 to register 234 and then to register 236.

Input lines READ, WRITE, and MMIO CS to diagnostic data port 100 are driven by a DSP memory controller within integrated circuit 150. Input line READ carries a read strobe signal while input line WRITE carries a write strobe signal. The signal on line MMIO CS is the memory mapped I/O chip select signal. The signals on these lines along with the address on the DSP address bus determine the register that is accessed with diagnostic data port 100 and whether the access is a read or a write.

Firmware internal to DSP 110 controls the information written to registers 232, 234 and 236. An example of firmware to assist in testing and optimizing a digital control tracking system is given in Appendix A and is described more completely below.

To utilize diagnostic data port 100, the firmware instructs DSP 110 to write the desired information to registers 232, 234, and 236. To start the serial transfer of the information to output pin DDO, DSP 110 writes to control register 231. The information is serially shifted out of registers 236, 234, and 232 to pin DDO on each falling edge of the diagnostic clock starting with the most significant bit (MSB) of register 236 and ending with the least significant bit (LSB) of register 232.

In this embodiment, the frequency of the diagnostic clock on line BCLOCK2 and on pin DCO is one-fourth the frequency of the system clock for integrated circuit 150 and one-half the frequency of the bus clock for DSP 110. With a 40 MHz system clock, this configuration gives a serial bit rate of 10 MHz for diagnostic data port 100 which is a reasonable rate for wire transmission and a rate that can be decoded without requiring special techniques. Of course, diagnostic data port 100 could be clocked at the frequency of the bus clock if that was desirable.

Typically, the information is shifted out to a stand-alone diagnostic interface board containing a shift/latch control circuit as well as digital-to analog converters, logic analyzer connections, oscilloscope test points and so on. The rising edge of the clock signal on pin DCO is used to shift the data on line DDO into a shift register on the stand alone board.

FIG. 3 is a block diagram of one embodiment of a stand alone diagnostic interface board 300 suitable for use with diagnostic data port 100. Board 300 performs a serial to parallel conversion of the information from diagnostic data port 100 and generates one 16-bit digital channel and two 12-bit resolution analog channels. Hence, to use diagnostic interface board 300, the word written in register 236 by DSP 110 is digital data while the digital words written in registers 234 and 232 represent analog data.

On board 300, the serial data from pin DDO and the clock signal from pin DCO are initially processed by shift/latch control logic 301. FIG. 4 is a more detailed schematic of one embodiment of shift/latch control logic 301. The information from pin DDO, i.e., the data, is buffered by shift/latch control circuit 301 and applied via line DATA to the serial input terminal of register 332.

The diagnostic clock signal is also buffered by shift/latch control circuit 301 and applied via line SHIFT to terminal CLK of registers 332, 334 and 336. The inverse of the diagnostic clock signal is applied to active low clear terminals CL of D-type flip-flops 405 and 406, which are used in generation of a latch pulse as described below.

Thus, the digital word from register 236 is serially shifted through registers 332 and 334 to register 336. Analog channels 1 and 2 are the second and third words shifted into register 334 and 332 respectively. In one embodiment, registers 332 to 336 are each a type 74AC164 register.

When the 48-bits have been shifted into registers 332 to 336, shift/latch control circuit 301 generates a latch pulse to store the three-sixteen bit words in a parallel format in D/A converter 342, D/A converter 344, and latch 346, respectively. For the circuit shown in FIG. 4, the latch pulse is generated when the clock signal from pin DCO remains low for a predetermined period, which in this embodiment is 1.0 .mu.s.+-.0.5 .mu.s.

Specifically, in shift/latch control circuit 301, the data on input pin DDOIN is buffered by inverters 410 and 411 and supplied over line DATA to shift register 332. Similarly, the clock signal on input pin DCOIN is buffered by inverters 412 and 413 and the signal from inverter 413 drives line SHIFT to registers 332, 334, and 336. The output signal of inverter 412 is applied to the active low clear terminals CL of D-type flip-flops 405 and 406. Thus, when there is a clock signal on pin DCOIN, flip-flops 405 and 406 are cleared every clock cycle.

An inverted pulse from inverter 404, that is generated by the signal from 1.00 MHz oscillator 403, is applied to terminals CLK of D-type flip-flops 405 and 406. A logic one signal is applied to input terminal D of flip-flop 405 and output terminal Q of flip-flop 405 is connected to input terminal D of flip-flop 406. Hence, on a first rising edge from inverter 404, a logic one is loaded into flip-flop 405 and on the next rising edge from inverter 404, the logic one would be clocked into flip-flop 406. However, the frequency of oscillator 403 is less than the clock frequency on pin DCOIN. Thus, both flip-flops 405 and 406 are cleared so that the logic one is not loaded into flip-flop 406 so long as there is a clock signal on pin DCOIN.

When the clock signal on pin DCOIN stops, the logic one in flip-flop 405 is loaded into flip-flop 406. The resulting rising edge from output terminal Q of flip-flop 406 is buffered by inverters 407 and 408. The output signal of buffer 408 clocks a logic one into D-type flip-flop 409 that in turn generates a latch pulse on output terminal Q because an active low clear terminal of flip-flop 409 is connected to the output terminal of inverter 404. The latch pulse is available at test point TP21.

Shift/latch control circuit 301 is an important aspect of this invention because shift/latch control circuit 301 eliminates the need for a three wire synchronous interface. Specifically, as described above, a latch signal on diagnostic interface board 300 is generated by detecting that the input clock sequence has stopped after the input clock sequence was started. Typically, in a three wire synchronous interface, the third wire carries a shift enable versus a latch signal. However, with shift/latch control circuit 301, only two-wires are required for diagnostic data port 100. This is a significant improvement, because it reduces the number of pins of integrated circuit 150 that are needed to support port 100. As is known to those skilled in the art, as the integration on a chip increases, one of the limiting factors is the number of pins on the integrated circuit.

When the digital word is latched in latch 346, the 16-bits are displayed on bit oriented display by LED and LED drivers circuit 348. The digital word is also available on 16 digital test points 350 that may be used for triggering external test equipment or captured as data to display events or states internal to integrated circuit 150.

When the two digital words representing analog data are latched in digital-to-analog converters 342 and 344, two corresponding analog voltages are generated by the 12-bit D/A two's complement converters. In this embodiment, each 12-bit D/A converter 342, 344 is aligned with the 12 most significant bits of the latched digital word. The two's complement conversion scaling of D/A converters 342 and 344 is illustrated in Table 1. ______________________________________ D/A TWO'S COMPLEMENT CONVERSION SCALING DATA WORD               OUTPUT VOLTAGE ______________________________________ MSB       LSB 0111 1111 1111 XXXX +5.0 VOLTS 0000 0000 0000 XXXX 0.0 VOLTS 1000 0000 0000 XXXX -5.0 VOLTS ______________________________________

The analog output voltages of D/A converters 342 and 344 are available on BNC analog out channel 1 and channel 2 connectors and on test points. These voltages can be analyzed by external test equipment to determine internal variable values or control loop characteristics within integrated circuit 150.

In this embodiment, diagnostic interface board 300 contains other hardware which may be used with this invention, but is not essential to the invention. The additional hardware is included only to demonstrate the usefulness of diagnostic data port 100 in monitoring internal functions of integrated circuit 150.

A digital shift register (SR) port connector and drivers are provided to support interfacing to a logic analyzer for other monitoring functions. The sixteen bits in shift register 332 are provided on digital SR port connector plus a clock that goes positive when the word is latched in D/A converter 342. Here, a positive edge is used because the positive edge marks the point in time where the data in shift register 332 is stable.

A RS-232 to/from logic level translator circuit 360 on diagnostic interface board 300 interfaces with output pins RX and TX of debug RS-232 serial port 111 of integrated circuit 150. Circuit 360 permits connection of a standard terminal or a computer in terminal mode to integrated circuit 150. In this embodiment, circuit 360 includes an integrated circuit Model No. AD232JR that is sold by Analog Devices of One Technology Way, P.O. Box 9106, Norwood, Mass. 02062-9106.

A system reset button and circuit on diagnostic interface board 300 generates an active low reset signal that can be applied to a reset pin of integrated circuit 150.

FIG. 5 is a schematic diagram of an analog translation amplifier 380. Analog translation amplifier 380 is not required for diagnostic data port 100. Analog translation amplifier 380 is an example of a circuit that can be included on board 300 to test an integrated circuit. In this case, analog translation amplifier 380 is described in conjunction with features of analog data acquisition system 116. As explained more completely below, analog translation amplifier 380 generates signals that can be used by analog data acquisition system 116. DSP 110 could be programmed to write data from the analog data acquisition system 116 to diagnostic data port 100 and in this way operations of specific features of analog data acquisition system 116 could be observed.

In FIG. 5, line CH.sub.-- X.sub.-- REF is connected to output pin VREFL of integrated circuit 150 that is driven by circuitry in analog data acquisition system 116 that is described more completely in copending, commonly filed and commonly assigned U.S. patent application Ser. No. 08/273,973, entitled "Analog Data Acquisition System For Servo Position Bursts" of John P. Hill, that was referenced above. Output pin VREFL supplies the center voltage for the swing of analog voltages in analog data acquisition system 116.

Analog translation amplifier 380 shifts the ground reference level of the input analog signal on line CH.sub.-- X.sub.-- IN that is referenced to or centered about a ground level that is selected by positioning switch S1. When switch S1 is placed in position EXT, the analog signal on line CH.sub.-- X.sub.-- IN is DC level shifted so that the analog signal is centered around the voltage on pin VREFL and the resulting voltage is ouput on line CHANX. Conversely, when switch S1 is placed in position INT, the output analog signal on line CHANX is DC level shifted around the analog voltage supplied by a channel X level control circuit CH.sub.-- X.sub.-- LVL. Analog translation amplifier 380 is useful for interfacing ground referenced test equipment to single supply systems. In this embodiment, the output analog signal on line CHANX is connected to input pin CHX of integrated circuit 150. Input pin CHX provides an input signal to the analog data acquisition system 116 and so the output analog signal on line CHANX may be used to characterize the control systems.

The operation of both diagnostic data port 100 and diagnostic interface board 300 depends on the firmware used in integrated circuit 150 to load registers. Appendix A is a listing of firmware that can be used with diagnostic data port 100 and diagnostic interface board 300 to test and optimize a digital control tracking system. Appendix A is only an illustration of the use of the invention and is not intended to limit the invention to the particular applications provided by the software. Moreover, the particular language used is a function of the microcontroller, DSP, or microprocessor controlling the system on which diagnostic data port 100 is incorporated. For a particular microcontroller, DSP, or microprocessor, the instructions necessary to read data in one location and write that data to diagnostic data port 100, or to read data in diagnostic data port 100 will be apparent to those skilled in the art. In Appendix A, the language is for DSP 110 and is similar to assembly language for a microcontroller.

FIG. 6 is a more detailed diagram of diagnostic data port 100 of this invention. Lines MMIO CS, READ, WRITE and 16-bit DSP address bus from the DSP memory controller drive an address decoder circuit 610. Address decoder circuit 610 is connected to load terminal LD and output enable terminal OE of each of registers 232, 234, and 236. Thus, in response to a write sequence of signals from the DSP memory controller, address decoder circuit 610 generates an active signal on each of load terminals LD so that 16-bits of data can be loaded into each of registers 232, 234, 236 from the DSP data bus.

Similarly, in response to a read sequence of signals from the DSP memory controller, address decoder circuit 610 generates an active signal on the output enable terminals OE so that data in the addressed register can be transferred to the DSP data bus. When the DSP writes to SR flip-flop 631, which in this embodiment is control register 231, address decoder circuit 610 generates an active signal on line 611 to terminal S of SR flip-flop 631. In response to the active signal on terminal S, SR flip-flop 631 generates an active signal on output terminal Q and an inactive signal on output terminal Q.

The active signal from output terminal Q drives a first input terminal of AND gate 612. A second input terminal of AND gate 612 is driven by the clock signal on line BCLOCK2. Thus, in response to the active signal from output terminal Q, AND gate 612 passes the clock signal to terminal CLK of a 6-bit down counter 620 that was previously loaded with a value of 48.

The output signal from AND gate 612 also drives output pin DCO and an input terminal of inverter 615. The output signal of inverter 615 drives terminal SHIFT of each of registers 232, 234 and 236. Thus, on each rising edge of the clock signal on line BCLOCK2, counter 620 is decremented, and for each falling edge, a bit is shifted in registers 236, 234 and 232.

When the value of counter 620 is zero, the output signal of NOR gate 621 generates an active signal on terminal R of SR flip-flop 631. In response to the active signal on terminal R, SR flip-flop generates an active signal on output terminal Q and an inactive signal on output terminal Q. The active signal on output terminal Q reloads counter 620. The inactive signal on terminal Q causes AND gate 612 to mask the clock signal and so operation of diagnostic data port 100 is suspended until DSP 110 again writes to SR flip-flop 631.

In this embodiment, counter 620 is loaded with a value of 48 and so the information in all three registers 232, 234 and 236 is shifted out on pin DDO. However, in another embodiment, counter 620 is a programmable counter and can be loaded with a value of 16, 32, or 48. In this case, data can be shifted from one, two or three of the registers. No other modifications are required, because shift/latch control circuit 301 automatically latches the data, as described above.

The firmware listing in Appendix A is an example of one use of this invention that is intended to help test and optimize a digital control tracking system. A brief description of Appendix A follows.

In the initialization code, upon reset of integrated circuit 150, a pointer is initialized to the storage location of the digital data that is written to register 236 in diagnostic data port 100. Similarly, two pointers are initialized to the storage locations of analog data that are written to registers 234 and 232 in diagnostic data port 100. In addition, for each of the two analog signals, an analog gain and an analog offset are defined. The default values for the analog offset are zero and for the analog gains are 1.0. A gain variable of 0.times.0010 is defined as a gain of one. The scaling and multiply operations with that gain varaiable align the most significant bit of the register (D15) with the most significant bit of the D/A converter (D11). This scaling allows gain settings greater and less than 1.

In this embodiment, the digital data pointer addresses a state/status word that shows the present state of a tracking servo system. The pointer for the first analog channel addresses a tracking actuator position error and the pointer for the second analog channel addresses a tracking actuator velocity.

The three address pointers, the two analog gains, and the two offsets can be changed in one embodiment by commands from a computer in terminal mode that is connected to RS-232 port 111 of integrated circuit 150 via circuits 360 of diagnostic interface board 300. The use of a RS-232 port is illustrative only. The commands could be supplied over any port of the integrated circuit. In this embodiment, the commands are implemented within integrated circuit 150 by an extended set of monitor software that is loaded in memory of DSP 110.

Table 2 illustrates information about command OS. In Table 2, as well as in Tables 3 to 7, in the first row, the first column is the command; the second and third columns are parameters for the command; and the fourth column is a brief description of the function performed by the command. Following the first row is an example of using the command. The characters to the left of ">" and the ">" are a prompt to the user. ______________________________________ OS  xxxx  yyyy  send data over Diagnostic Outport Example: OOFF2> OS ______________________________________

Command OS sends the data as specified by the commands OA, OG, OP, and OR, that are described more completely below, over diagnostic data port 100, i.e., in response to command OS, DSP 110 writes to control register 231. Parameters xxxx and yyyy are not used in command OS and no status is displayed. ______________________________________ OA  n  aaaa   address aaaa contains data to be used in diag outport register n Example: OOFF2> OA 0 1234 ______________________________________

Command OA sets a pointer to a memory location and when command OS or OD is initiated, the pointer is read to determine the memory location from which to get the data. Valid values of parameter n are zero, one and two. Parameter n is the diagnostic outport register identification, i.e., the identification for one of registers 232 to 236. Parameter aaaa is the address of the data. No status information is displayed. ______________________________________ OD  xxxx  yyyy display diag outport selections (addr or register, offset, and gain) ______________________________________

A:) Data is retrieved from any memory location with the data memory address space: OOFF2> OD Addr/Reg Addr/Reg Ptr      Data      Offset    Gain ______________________________________ DD00     3000       45        10      2 DD01     3001       1234      0       10 DD02     3002       AAAA      n/a     n/a ______________________________________

B:) Data is retrieved from registers that are not in the data memory address space: OOFF2> OD Addr/Reg Addr/Red Ptr      Data      Offset    Gain ______________________________________ DD00     ext0       45        10      2 DD01     ext3       1234      0       10 DD02     ext4       AAAA      n/a     n/a ______________________________________

C;) Data is retrieved from any memory location with the data memory address space and from registers that are not in the data memory address space: OOFF2> OD Addr/Reg Addr/Red Ptr      Data      Offset    Gain ______________________________________ DD00     4095       45        10      2 DD01     ext3       1234      0       10 DD02     699A       AAAA      n/a     n/a ______________________________________

Command OD displays the diagnostic data port settings as specified by commands OA, OG, OO, and OR. Parameters xxxx and yyyy are not used and on status is displayed. In the examples of Table 4, command OD is shown for retrieving data from within and outside the data memory address space. Following the command is the data send that is displayed on the monitor connected to board 300. The left most column in the display is a designation for each of the registers in diagnostic data port 100. ______________________________________ OG  n  vvvv    gain vvvv to multiply diagnostic outport register n data Example: OOFF2> OG 0 10 ______________________________________

Command OG allows the user to specify a gain that is applied to the analog data copied to one of analog diagnostic output registers 232 and 234. Parameter n is the analog diagnostic outport register for which the gain is applied. In this embodiment, valid values for parameter n are zero and one. Parameter vvvv is the value of the gain to be applied to the data. No status is displayed. ______________________________________ OO  n  vvvv    offset vvvv to add to diagnostic outport register n data Example: OOFF2> OO 0 50 ______________________________________

Command OO allows the user to specify an offset that is applied to the analog data copied to one of analog diagnostic output registers 232 and 234. Parameter n is the analog diagnostic outport register for which the offset is applied. In this embodiment, valid values for parameter n are zero and one. Parameter vvvv is the value of the offset to be applied to the data. No status is displayed. ______________________________________ OR  n  m      external reg m data to be used in diagnostic outport register n Example: OOFF2> OR 0 4 ______________________________________

Command OR is used to specify that the data copied to a diagnostic data outport register 232, 234, and 236 is retrieved from an external register, i.e., a register that is not in the data memory address space. Parameter n is the diagnostic data output register into which the data is copied, and valid values are zero through two. Parameter m is the external register from whence the data is copied and valid values are zero through five. No status is displayed.

Hence, in this embodiment, the above serial port commands are implemented to allow the user to change the value of any one or all of the three address pointers, the two analog gains, and the two offsets.

The servo burst interrupt code module in Appendix A is called at each servo bust interrupt after the time-critical functions have been processed. All diagnostic data output registers 232, 234 and 236 are updated, and therefore diagnostic interface board 300 outputs data at the sample rate of the servo system, i.e., real time sampled data is obtained from diagnostic data port 100 for internal functions of integrated circuit 150.

In this example, the digital channel address pointer is read to determine the memory location from which the data is copied to register 236. The analog channel 1 address pointer is then read and that data at that memory location is accessed. The analog channel 1 offset value is then read and added to the data retrieved from the specified memory location. The result is multiplied by the analog channel 1 gain with the appropriate scaling shifts. (0.times.0010=1X) Analog diagnostic data output register 234 is then loaded with the result. The data for analog channel 2 is then processed in a similar manner to the data for analog channel 1 and the result written to analog diagnostic data output register 232. Finally, DSP 110 writes to diagnostic control register 231 with any value to start the hardware controlled data output sequence from diagnostic data port 100.

The output signal of translation amplifier 380 on diagnostic interface board 300 to the channel X input pin of integrated circuit 150 can be used to input a disturbance from a dynamic signal analyzer (DSA). Integrated circuit 150 could be programmed to add the signal from channel X input pin to an internal control loop error signal. The internal control loop error signal before and after the addition can be sent to diagnostic data port 100 and consequently to the DSA, which in turn allows a transfer function of the loop to be measured.

Outputting signals that represent "physical" variables such as "Tracking Position Error" or "Spin Period Error" through the analog channels of diagnostic data port 100 provides a means for a spectrum analyzer to analyze system dynamics. To analyze small perturbations of variables that have large average values, the average value can be subtracted out using the analog channel offset variable and then the perturbation can be magnified using the analog gain variable.

Other applications of diagnostic data port 100 include outputting an analog type variable and displaying the analog type variable on digital display 348 to verify shifting operations or alignment. A digital type variable can be output and displayed as an analog waveform to display sequences of states on an oscilloscope. Alternatively, two digital type variables can be output on the analog channels and displayed on a scope in an X/Y mode to generate a state space type display.

The embodiment of the diagnostic data port and the diagnostic board described above are only illustrative of the principles of this invention are not intended to limit the invention to the particular embodiment disclosed. In view of this disclosure, those skilled in the art can implement the two-wire dedicated diagnostic data port in a wide variety of integrated circuits and in a wide variety of configurations to achieve the advantages described above. ##SPC1##

## Claims

1. In an integrated circuit, a two-pin diagnostic data port comprising: processor address bus, and said serially connected memory having a serial clock terminal and a serial output terminal processor data and address busses; and to a clock signal on said serial clock terminal; serial clock terminal wherein said first pin is a first pin of said two-pin diagnostic port; and second output pin is a second pin of said two-pin diagnostic port.

2. In an integrated circuit, the two-pin diagnostic data port of claim 1 further comprising: said processor data and address busses wherein upon writing to said control register, said clock signal is applied to said serial clock terminal of said serially connected memory and to said first output pin.

3. In an integrated circuit, the two-pin diagnostic data port of claim 1 further comprising: output pin.

4. In an integrated circuit, a two-pin diagnostic data port as in claim 1 wherein said serially connected memory comprises a plurality of serially connected registers.

5. In an integrated circuit, a two-pin diagnostic data port as in claim 4 wherein said plurality of serially connected registers comprises three serially connected sixteen bit registers.

6. In an integrated circuit, a two-pin diagnostic data port as in claim 3 wherein said serially connected memory further comprises a shift terminal, and further wherein said clock input line is coupled to said shift terminal.

7. In an integrated circuit, a two-pin diagnostic data port as in claim 1 further comprising: decoder circuit loads data from said processor data bus into said serially connected memory, and decoder circuit transfers data from said serially connected memory to said processor data bus.

8. In an integrated circuit, a two-pin diagnostic data port as in claim 7, wherein said serially connected memory comprises a plurality of serially connected registers.