Initiating FPGA Reconfiguration from Microcontroller JTAG

[dhthomas]

I know that there are some application notes (XAPP058, XAPP424) that deal with playing back a file over JTAG, but what I want to do is much simpler than that. I would like to send a command to a PROM that re-initiates FPGA configuration for the FPGA that is is connected to. Like a power-on reset, where the entire FPGA is reprogrammed.

According to the Platform Flash User Guide (UG161),

"The Platform Flash PROM can initiate an FPGA configuration. When a JTAG CONFIG
instruction is updated into the Platform Flash PROM, the Platform Flash PROM
temporarily drives its CF pin Low followed with a very brief drive to a High. Combined
with an external pull-up resistor on the CF pin, this generates a High-Low-High pulse out
of the CF pin that can be used to pulse the FPGA PROGRAM (or PROG_B) pin. The pulse
to the FPGA PROG_B pin initiates the FPGA configuration sequence."

But it doesn't go into any more detail of how to do that.

Any pointers?

[iguo]

Send the CONFIG command into PROM through its JTAG ports; you can find the CONFIG command in the PROM's BSDL file.

Message Edited by iguo on 02-17-2009 01:16 AM

[lfournier]

Hi Iguo,

I assume that is enough longer that post was wrote but I would like to know if the following instructions (from XSVF file) are quite good to send the CONFIG command. For information, after reading the PROM datasheet, the CONFIG command seems to be 0xEE. So, I tried to write the XSVF command and it will be like this:

XREPEAT 0x20
XSTATE 0x00 // Test-Logic-Reset state
XSTATE 0x01 // Run-Test/Idle
XRUNTEST 0x00000000
XSIR 0x08 0xEE // CONFIG instruction
XSDRTDO 0x00 0x00 // No TDO expected ?
XCOMPLETE

I don't really know if this sequence is good or not... Feel free to any suggestion, it will be really really helpful !