We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 8905

3.1i JTAG Programmer - When can I assign a USERCODE to a device for readback through the JTAG Programmer?


Keywords: JTAG Programmer, 3.1i, 2.1i, USERCODE, userid, grey, gray

Urgency: Standard

General Description:
The JTAG Programmer has the capability to read the USERCODE from a device. Why is this greyed out when I target FPGAs?


Certain FPGAs support the JTAG USERCODE instruction; those FPGAs that have a USERCODE register can be configured to store a specific value in this register. However, the USERCODE must be configured at the time the bit stream is created. Once the bit stream is generated, there is no way to modify the USERCODE without regenerating the bit stream.

The supported devices are:
Spartan-II, Virtex, Virtex-E, Virtex-II

18v00 PROMs
The 18v00-series PROMs support the JTAG USERCODE instruction. The USERCODE register can be configured directly through the JTAG Programmer by entering in the desired USERCODE value. To reconfigure this USERCODE register, the 18v00 PROM can simply be reconfigured.

All XC9500 CPLDs have USERCODEs that must be specified when the JEDEC file is created.
AR# 8905
Date Created 08/31/2007
Last Updated 09/30/2005
Status Archive