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Method and Apparatus for Automatic Identification and Testing of a Plurality of IEEE 1149.1 JTAG Interfaces in a System or Tester

IP.com Disclosure Number: IPCOM000022290D
Original Publication Date: 2004-Mar-05
Included in the Prior Art Database: 2004-Mar-05
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Abstract

IEEE 1149.1 JTAG interface checking has historically been performed in a system through a series of software commands. This method has overhead in development, verification, and IPL time. As with most system testing, it is desirable to move the function into hardware test engines, minimizing this overhead. Hereafter describes that hardware implementation.

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Method and Apparatus for Automatic Identification and Testing of a Plurality of IEEE
1149.1 JTAG Interfaces in a System or Tester

The IEEE 1149.1 standard defines a few basic functions that all chips designed within the standard must implement. A test designed only using these instructions should work for all hardware following the standard. This test would then be portable to other designs, faster than a software driven test and require little repeat verification.

     The automated interface existence checking sequencer below steps through each possible interface (refer to the figure below). Steps 0 - 1 reset all interfaces through the homing sequence (all JTAG interfaces return to RUNTESTIDLE with 5 TCKs while TMS is high) The transition to Step 1 also resets the DONE bit and sets the INPROGRESS bit in the checking status register.

Steps 2 - 14 are looped through for each interface. Steps 2 - 9 put the selected interface in the BYPASS state. Steps 10 -12 scan 0's through that interface and check that 0's come back on TDO - logging an error against that interface if detected. Step 13 scans 1's through that interface and check that 1's come back on TDO - logging an error against that interface if detected. Step 14 re-homes all chips on this interface then loops back to Step 2 for more testing, or Step 0 (IDLE) if complete. The transition back to IDLE also sets the DONE bit and resets the INPROGRESS bit.

     This interface testing previously was purely a software task. Th...