Answers Database

BOUNDARY SCAN/JTAG: How to use EXTEST instruction before configuration in a XC4K/XC5K device?


Record #194

Problem Title:
BOUNDARY SCAN/JTAG: How to use EXTEST instruction before configuration
in a XC4K/XC5K device?



Problem Description:
Keywords: xc4000, xc5200, extest, program pin

Urgency: standard

General Description:
How to execute the EXTEST instruction before conficuration?


Solution 1:

If the /PROG pin is held low, the Boundary Scan registers for EXTEST
will reset. The correct way to use the EXTEST instruction is to
hold the INIT pin low to hold off the start of configuration and then,
execute the EXTEST instruction.

The only other way to use the EXTEST instruction is to do so after
configuration.





End of Record #194