Answers Database

BOUNDARY SCAN/JTAG: Latched instruction in the Test-Logic-Reset state ofXC4K/XC5K/XC9K parts


Record #2953

Product Family:  Hardware

Product Line:  4000

Problem Title:
BOUNDARY SCAN/JTAG: Latched instruction in the Test-Logic-Reset state
ofXC4K/XC5K/XC9K parts



Problem Description:
Keywords: test-logic-reset, XC4000, XC5200, xc9500, bypass, idcode

Urgency: standard

General Description: Which instruction gets latched into the XILINX
XC4K/XC5K/XC9K devices when the part is in the Test-Logic-Reset state.



Solution 1:

According to IEEE 1149.1, the default instruction that gets latched into
a part in the Test-Logic-Reset state is the IDCODE instruction. If this
instruction is not supported, then the BYPASS instruction gets latched.

In the XC4000 and XC5200 family parts, IDCODE instruction is not supported
and hence the BYPASS instruction gets latched.

In the XC9500 family parts, the IDCODE instruction gets latched.



End of Record #2953