AR# 15983

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Virtex-II/-II Pro - Boundary Scan (JTAG) tests fail when the Pause-IR state is used (Incorrect TDO value)

Description

When I use the Pause-IR functionality in a Virtex-II/-II Pro device, Boundary Scan (JTAG) tests fail (the Pause-IR state is used when a pause is needed while data is shifted into the instruction register).

If the TAP is moved to the Pause-IR state during a shift into the Shift-IR state, the first bit that is clocked out of TDO might be incorrect; however, subsequent bits will be correct.

Solution

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

AR# 15983
Date 12/15/2012
Status Active
Type General Article
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