Abstract:
A communication channel that is accessible when the product is entirely assembled, but appears to be, and functions like, configuration jumpers to the end user. The communication channel utilizes the terminals of a configuration jumper block as communication paths to an interface device. The terminals of the configuration jumper block may be wired differently depending on the desired function (i.e. send data, receive data, etc.) of the terminals. The configuration information needed by the device is read from the terminals of the configuration block when the communication channel is not active. Switches on the interface device are used to set the configuration information. Configuration jumpers that can be used are the Master, Slave, and Cable Select signals for an ATAPI interface.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to communicating data. More particularly, this invention relates to communicating data on signals that are normally static, such as configuration jumper signals. 
     BACKGROUND OF THE INVENTION 
     Many electronic devices have a communication channel that is used for development, diagnostic, and production functions. For example, a disk drive may have an RS-232 interface connected through a DB-9 connector so that a firmware developer can monitor the internal state and functioning of the disk drive. This same interface may also be used later in a production environment to initiate and monitor a final self-test sequence before packaging and shipping the device to a consumer. Unfortunately, a large connector, such as a DB-9 or DB-25, is unsightly, adds cost, and may be difficult to find room for on the product. Furthermore, it may be desirable to discourage the end user from accessing this interface. The connector can be hidden, and access prevented by placing the connector underneath the case, or skin, of the product. However, if the connector is hidden in this way, it is inaccessible when the product is completely assembled. This makes it impossible to access the communication product after a certain stage of manufacture, and impossible to access when the product is being used in it&#39;s intended manner. 
     Accordingly, there is a need in the art for a communication channel that can function after a product is entirely assembled, but does not advertise its presence. It is desirable that this channel not necessarily require an additional connector. Such a channel should also be capable of communicating both serial and parallel data in both directions. Finally, such a channel should be capable of implementation using existing features that are accessible from the outside of a filly assembled device. 
     SUMMARY OF THE INVENTION 
     The invention provides a communication channel that is accessible when the product is entirely assembled, but appears to be, and functions like, configuration jumpers to the end user. This communication channel requires only a small number of additional parts, and possibly even saves money by eliminating the need for a large, expensive connector on each device. The invention is readily adaptable to a variety of interfaces, both standard and non-standard. 
     An embodiment of a communication channel according to the invention utilizes the terminals of a configuration jumper block as communication paths to an interface device. The terminals of the configuration jumper block may be wired differently depending on the desired function (i.e. send data, receive data, etc.) of the terminals. The configuration information needed by the device is read from the terminals of the configuration block when the communication channel is not active. Switches on the interface device are used to set the configuration information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a communication path that can send and receive data to and from an interface device and a host device using a non-continuously sampled signal. 
     FIG. 2 is a schematic illustration of a communication path that can send data from an interface device to a host device using a non-continuously sampled signal. 
     FIG. 3 is a schematic illustration of a communication path that sets a non-continuously sampled signal either by jumper, or by switch on an interface device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Many electronic devices have signals that are sampled only once, or at most a few times during the devices normal operation. These are non-continuously sampled signals. Examples of this type of signal are signals set by a configuration jumper. These jumpers may set some internal configuration information, such as the device address or interrupt number, by determining that state of a set of signals when they are read during a power-up sequence. 
     FIG. 1 is a schematic illustration of a communication path that can send and receive data to and from an interface device and a host device using a non-continuously sampled signal. In FIG. 1, signal J 1  is a non-continuously sampled signal. The elements inside box  102  are on the host device. In FIG. 1 terminal  122  of connector  104  is coupled to a positive supply voltage. The other terminal of connector  104 , terminal  124 , connects to one terminal of resistor  108  and one terminal of resistor  106 . The other terminals of resistors  108  and  106  are connected to J 1  and a negative supply, respectively. In the preferred embodiment, resistor  108  is 1 KΩ and resistor  106  is 50 KΩ. During normal operation of the host device, jumper  112  may optionally connect the two terminals of connector  104 . If jumper  112  is not in place, signal J 1  is pulled down through resistors  108  and  106 . If jumper  112  is in place, terminal  124  is connected through jumper  112  to a positive supply voltage. This pulls signal J 1  high through resistor  108 . Resistor  106  prevents the positive supply from being shorted to the negative supply when jumper  112  is in place. 
     For the host to send data to an interface device, jumper  112 , if present, is removed. Connector  110  is then interfaced with connector  104  so that terminal  126  of connector  110  connects to terminal  122  and terminal  128  of connector  110  connects to terminal  124 . These connections are shown by dotted lines  116  and  114 , respectively. Connection  116  is optional but may be used to provide a positive supply voltage to the interface device. Connector  110 , resistor  120 , and switch S 1   118  are either on or connected to the interface device even when the interface device is not connected to the host device. One terminal of single-pole single-throw switch S 1   118  is connected to a positive supply voltage. The other terminal of switch S 1   118  is connected to a first terminal of resistor  120 . A second terminal of resistor  120  is connected to terminal  128  of connector  110 . This node is the DATA node. In the preferred embodiment, resistor  120  is 10 KΩ. When 
     The DATA node may be connected to an RS-232 interface device, a Universal Asynchronous/Synchronous Receiver Transmitter (USART), parallel interface port, or some other input/output device to receive or send data sent to and from the host device on signal J 1 . In the preferred embodiment, the DATA node is connected to an RS-232 interface device. 
     With connector  110  in place, the position of switch S 1   118  sets the value of signal J 1  when signal J 1  is sampled. After J 1  has been sampled, the host device may send data by overdriving the relatively high impedances of resistor  120  and  106  with a driver or buffer in series with the relatively low impedance of resistor  106 . A device on the interface device may send data to the host by overdriving resistor  120  and  106  with a driver or buffer connected to the DATA node. 
     In FIG. 1, terminal  122  is coupled to a positive supply voltage and resistor  106  is connected to a negative supply voltage. Alternatively, one of ordinary skill in the art would recognize that if terminal  122  were coupled to a negative supply voltage, and resistor  106  were connected to a positive supply voltage, then when jumper  112  was not in place, signal J 1  would be pulled high and when jumper  112  was in place, J 1  would be pulled low. Switch S 1   118  could then be connected to a negative supply voltage instead of a positive supply voltage to set the value of signal J 1  when signal J 1  is sampled. 
     FIG. 2 is a schematic illustration of a communication path that can send data from an interface device to a host device using a non-continuously sampled signal. In FIG. 2, signal J 2  is a non-continuously sampled signal. The elements inside box  202  are on the host device. In FIG. 2 terminal  222  of connector  204  is coupled to a positive supply voltage through resistor  208 . Terminal  222  is the RXD node of the host device. The other terminal of connector  204 , terminal  224 , is connected to signal J 2 , which also connects to one terminal of resistor  206 . The other terminal of resistor  206  is connected to a negative supply voltage. In the preferred embodiment, resistor  208  is 10 KΩ and resistor  206  is 50 KΩ. During normal operation of the host device, jumper  212  may optionally connect the two terminals of connector  204 . If jumper  212  is not in place, signal J 2  is pulled down through resistor  206 . If jumper  212  is in place, terminal  224  is pulled up through jumper  212  and resistor  208  to a positive supply voltage. This pulls signal J 2  high. Resistor  206  prevents the positive supply from being shorted to the negative supply when jumper  212  is in place. 
     For the interface device to send data to host, jumper  212 , if present, is removed. Connector  210  is then interfaced with connector  204  so that terminal  226  of connector  210  connects to terminal  222  and terminal  228  of connector  210  connects to terminal  224 . These connections are shown by dotted lines  216  and  214 , respectively. Connector  210  and switch S 2   220  either are on or connected to the interface device even when the interface device is not connected to the host device. One terminal of single-pole single-throw switch S 2   220  is connected to terminal  226  which is the TRANSMIT DATA node. The other terminal of switch S 2   220  is connected to terminal  228 . Data is placed by the interface device on signal TRANSMIT DATA and is received by the host device on node RXD. 
     The TRANSMIT DATA node may be connected to an RS-232 interface device, a Universal Asynchronous/Synchronous Receiver Transmitter (USART), parallel interface port, or some other input/output device to send data sent to the host device. In the preferred embodiment, the TRANSMIT DATA node is connected to an RS-232 interface device. 
     With connector  210  in place, the position of switch S 2   220  sets the value of signal J 2  when signal J 2  is sampled. To function properly, the TRANSMIT DATA node should be held high until J 2  has been sampled. In the preferred embodiment, this is easily accomplished since the idle state of an RS-232 line is defined to be high. After J 2  has been sampled, the interface device may send data by overdriving the relatively high impedances of resistors  208  and  206  with a driver or buffer. 
     In FIG. 2, terminal  222  is coupled to a positive supply voltage through resistor  208  and resistor  206  is connected to a negative supply voltage. Alternatively, one of ordinary skill in the art would recognize that if terminal  222  were coupled to a negative supply voltage, and resistor  206  were connected to a positive supply voltage, then when jumper  212  was not in place, signal J 2  would be pulled high and when jumper  212  was in place, J 2  would be pulled low. The TRANSMIT DATA node would then need to be held low until after the sampling of J 2 . 
     FIG. 3 is a schematic illustration of a communication path that sets a non-continuously sampled signal either by jumper, or by switch on an interface device. In FIG. 3, signal J 3  is a non-continuously sampled signal. The elements inside box  302  are on the host device. In FIG. 3 terminal  322  of connector  304  is coupled to a negative supply voltage. The other terminal of connector  304 , terminal  324 , is connected to signal J 3 , which also connects to one terminal of resistor  306 . The other terminal of resistor  306  is connected to a positive supply voltage. In the preferred embodiment, resistor  306  is 10 KΩ. During normal operation of the host device, jumper  312  may optionally connect the two terminals of connector  304 . If jumper  312  is not in place, signal J 3  is pulled up through resistor  206 . If jumper  312  is in place, terminal  324  is pulled down through jumper  312  by a negative supply voltage. This pulls signal J 3  low. Resistor  306  prevents the positive supply from being shorted to the negative supply when jumper  312  is in place. 
     For the interface device to set the value of J 3 , jumper  312 , if present, is removed. Connector  310  is then interfaced with connector  304  so that terminal  326  of connector  310  connects to terminal  322  and terminal  328  of connector  310  connects to terminal  324 . These connections are shown by dotted lines  316  and  314 , respectively. Connection  316  is optional, but may be used to establish a common reference level, or provide a negative supply voltage to the interface device. Connector  310  and switch S 3   320  either are on or connected to the interface device even when the interface device is not connected to the host device. One terminal of single-pole single-throw switch S 3   320  is connected to terminal  328 , which is also the J 3  signal node. The other terminal of switch S 3   320  is connected to a negative supply. With connector  310  in place, the position of switch S 3   320  sets the value of signal J 3  when signal J 3  is sampled. 
     In FIG. 3, terminal  322  is coupled to a negative supply voltage. Alternatively, one of ordinary skill in the art would recognize that if terminal  322  were coupled to a positive supply voltage, and resistor  306  were connected to a negative supply voltage, then when jumper  312  was not in place, signal J 3  would be pulled low and when jumper  312  was in place, J 3  would be pulled high. 
     In the preferred embodiment, the host device has an AT Attachment Packet Interface (ATAPI) channel as one interface to a host computer. Many devices that have ATAPI channel have configuration jumpers to set the ATAPI Master, Slave, and Cable Select configuration. In the preferred embodiment, these configuration jumpers are sampled only on power up and are used with the communication paths described in FIGS. 1,  2 , and  3  to provide a bi-directional RS-232 communication channel between the host device and an interface device. This secondary RS-232 link may be used for development, diagnostic, and production functions without requiring the skin of the host device be removed to access a special connector. In the preferred embodiment, the Master configuration jumper terminals are used to send data from the host device to the interface device. This is done using the circuitry and communication path shown in FIG.  1 . The Slave configuration jumper terminals are used to send data from the interface device to the host device. This is done using the circuitry and communication path shown in FIG.  2 . The Cable Select configuration jumper terminals are set by a switch on the interface device using the circuitry and communication path shown in FIG.  3 . 
     Although several specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The invention is limited only by the claims.