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AR# 22539

Platform Flash PROM (XCF08P/XCF16P/XCF32P) - Boundary Scan (JTAG) tests fail when the Pause-IR or Pause-DR states are used (Incorrect TDO value)

Description

When I use the Pause-IR or Pause-DR functionality in an XCF00P device, Boundary Scan (JTAG) tests fail. (The Pause-IR or Pause-DR state is used when a pause is needed while data is shifted into the instruction or data register.)

If the TAP is returned to the Shift-IR or Shift-DR state after a temporary pause in the Pause-IR or Pause-DR state, the contents of the shift register are corrupted because the shift register incorrectly recaptures its initial values.

Solution

To work around this problem, do not use the Pause-IR or Pause-DR state when scanning the instruction or data register. If a pause is required, TCK should be halted (this is often referred to as a "gated" TCK).

This issue is documented in the Platform Flash Data Sheet in the IEEE 1149.1 Boundary Scan (JTAG) section.

AR# 22539
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article