Extending synchronous busses by arbitrary lengths using native bus protocol

• US 6,507,920 B1
• Filed: 07/15/1999
• Issued: 01/14/2003
• Est. Priority Date: 07/15/1999
• Status: Expired due to Term

• Current Assignee: Teradyne Incorporated
• Original Assignee: Teradyne Incorporated
• Inventors: Truebenbach, Eric L.
• Primary Examiner(s): Beausoleil, Robert
• Assistant Examiner(s): Ziemer, Rita A
• Application Number:
  US09/354,137
• Time in Patent Office: 1,279 Days
• Field of Search: 714/43, 714/34, 327/51, 365/63, 365/194, 365/233, 710/100, 713/600, 712/225, 712/36
• US Class Current: 714/43
• CPC Class Codes: G01R 31/31722 Addressing or selecting of test units, e.g. transmission protocols for selecting test units for scan test G01R31/318558
• CPC Class Codes: G01R 31/31907 Modular tester, e.g. controlling and coordinating instruments in a bus based architecture
• CPC Class Codes: G06F 11/2221 to test input/output devices or peripheral units
• CPC Class Codes: G06F 13/4045 where the bus bridge performs an extender function

Abstract

A bus extender for extending synchronous busses of limited length provides convenient access to bus cards in ATE systems. The bus extender plugs into a synchronous bus, for example, a PCI bus, and a cable carries bus signals to a remote location, where a remote card is engaged. The bus extender supports both initiator (master) and target (slave) modes of the remote card, and communicates with the remote card in the native protocol of the bus. The bus extender operates without requiring separate control from the bus. For example, the bus extender does not require its own device driver. The bus extender includes a bus snooper circuit that monitors bus transactions with the remote card and stores configuration data. The bus snooper circuit responds locally on behalf of the remote card to bus requests that require rapid responses. The bus extender further includes a state machine that copies the stored configuration data to the remote card to reset the remote card without requiring a reset of the bus. A hold-off circuit is also included within the bus extender, which determines a hold-off interval required for return signals from the remote card to settle. The hold-off circuit receives the return signals applies them to the bus after the hold-off interval elapses.

Claims

1. A method of extending a synchronous bus using an extender device that physically engages the synchronous bus, the method comprising the extender device:

receiving a plurality of bus signals from the synchronous bus and driving the plurality of bus signals to a remote device via an interconnect, the interconnect having an arbitrarily long length;

receiving return signals from the remote device over the interconnect, the return signals having a settling time that varies in relation to the length of the interconnect;

establishing a hold-off interval, at least as long as the settling time of the return signals; and

applying the return signals to the synchronous bus after the hold-off interval elapses,

thereby ensuring that the return signals settle before they are applied to the synchronous bus, regardless of the length of the interconnect.

2. The method of claim 1, wherein the step of establishing the hold-off interval comprises the extender device:

activating the remote device to generate return signals; and

counting a number of sample clocks until the return signals settle.

3. The method of claim 2, wherein the step of activating the remote device to generate return signals comprises issuing a REAL) instruction to the remote device.

4. The method of claim 1, wherein the step of establishing the hold-off interval comprises setting the hold-off interval to a standard interval long enough to accommodate a range of interconnect lengths.

5. The method of claim 1, further comprising the extender device:

monitoring the synchronous bus to detect a transaction with the remote device; and

storing the trans action with the remote device.

6. The method of claim 5, wherein the transaction detected in the monitoring step is a WRITE instruction to the remote device, and the step of storing the transaction includes building a record indicative of a configuration of the remote device.

7. The method of claim 6, wherein the remote device is a first remote device, and further comprising:

restoring the record indicative of the configuration of the remote device onto one of the first remote device and a second remote device, to precondition for operation said one of the first remote device and second remote device.

8. The method of claim 5, wherein the step of monitoring the synchronous bus includes detecting a condition on the synchronous bus to which a rapid response is required, and applying a rapid response to satisfy the condition on behalf of the remote device.

9. The method of claim 1, further comprising controllably applying and removing power to the remote device.

10. A method of extending a synchronous bus using an extender device that physically engages the synchronous bus, the method comprising the extender device:

monitoring the synchronous bus to detect a transaction with a remote device, the transaction including contents that encode a configuration of the remote device; and

storing the contents of the transaction with the remote device, to maintain a local copy of the configuration of the remote device.

11. The method of claim 10, wherein the step of monitoring the synchronous bus further comprises:

detecting a condition on the synchronous bus to which a rapid response is required; and

applying a response to satisfy the condition on behalf of the remote device.

12. The method of claim 10, wherein the remote device is a first remote device, and further comprising restoring the local copy of the configuration of the remote device onto one of the first remote device and a second remote device, to precondition for operation said one of the first remote device and second remote device.

13. A method of testing UUTs that are synchronous bus cards, comprising:

building a record of configuration data for a first UUT;

blocking a flow of power between the synchronous bus and the first UUT until a time after a second UUT is installed; and

copying the record of configuration data for the first UUT onto the second UUT before proceeding to test the second UUT,

thereby allowing UUTs to be exchanged safely while the synchronous bus remains operative.

14. The method of claim 13, further comprising detecting a fault on a UUT and informing an ATE controller that the fault has occurred.

15. The method of claim 14, wherein the step of informing includes communicating the fault to the ATE controller via the synchronous bus.

16. The method of claim 14, wherein the step of informing includes communicating the fault to the ATE controller via a channel that is physically distinct from the synchronous bus.

17. A bus extender for extending a synchronous bus to facilitate the testing of synchronous bus cards, comprising:

an extender device coupled to the synchronous bus; and

an interconnect, coupled to the extender device and extending over a length to a connector arranged to engage a UUT,

wherein the extender device includes a hold-off circuit, coupled to the interconnect and the synchronous bus, the hold-off circuit including—

a delay register for storing a hold-off interval based upon the length of the interconnect; and

a delay circuit for preventing return signals that arrive from the UUT from asserting onto the synchronous bus until the hold-off interval elapses.

18. The bus extender of claim 17, wherein the hold-off circuit includes a delay determination circuit, comprising:

a signal sampler, coupled to the interconnect that samples the return signals to determine a number of sample clocks required for the return signals to settle, and stores the result in the delay register; and

a strobe circuit, coupled to the delay register and the delay circuit, that waits until the number of sample clocks stored in the delay register elapse, and activates the delay circuit to release the return signals to the synchronous bus.

19. The bus extender of claim 17, wherein the extender device further comprises a bus snooper circuit, the bus snooper circuit comprising:

a bus decoder, coupled to the synchronous bus that detects a transaction with the UUT; and

a remote status memory, coupled to the bus decoder and the remote bus interface, that stores the transaction with the UUT.

20. The bus extender of claim 17, wherein the transaction detected by the bus decoder is a WRITE instruction to the UUT, and the remote status memory stores a record indicative of a status of the UUT.

21. The bus extender of claim 20, wherein the UUT is a first UUT, and the extender device is constructed and arranged to copy the record for the first UUT to a second UUT to precondition the second UUT for operation.

22. The bus extender of claim 19, further comprising a local response generator, coupled to the synchronous bus, that detects a condition on the synchronous bus to which a rapid response is required and applies a rapid response to satisfy the condition.