AR# 194: JTAG - How to use EXTEST instruction before configuration in a XC4K/XC5K device?
AR# 194
JTAG - How to use EXTEST instruction before configuration in a XC4K/XC5K device?
Description
Keywords: xc4000, xc5200, extest, program pin, JTAG
Urgency: standard
General Description:
How to execute the EXTEST instruction before configuration?
Solution
If the /PROGRAM pin is held low, the Boundary Scan registers for EXTEST will reset and not work. Releasing /PROGRAM, but holding the INIT low will halt configuration just at the start. With the INIT signal held low, you may then execute the EXTEST instruction.
The only other way to use the EXTEST instruction is to do so after configuration has completed.