Answers Database

FPGA Configuration: How to reconfigure one 3k/4k device out of a daisy chain


Record #149

Problem Title:
FPGA Configuration: How to reconfigure one 3k/4k device out of a daisy
chain



Problem Description:



Solution 1:




It is some times necessary to reconfigure only one device in a daisy-chain of
fpgas.	This is possible, although it requires some modification of the
design.

The user-configurable pins that are also used as DIN and DOUT before
configuration should be wired together in the design, so that the connectivity
exists after configuration as well. Then, to reconfigure a device, provide
input at the first device in the chain (the usual source before configuration),
and pull program (4k) or done/program (3k) low on the device you wish to
reconfigure.  CCLK should be provided to the chips as it was during power-on
configuration.The data should ripple through the configured devices until it
is recieved by the device that is being reprogrammed.

If this method is used on a 3000, 3100, or 3000A part, the done/program lines
should not be connected together so that done/program on one device may be
pulled low independent of the others. On the 4000 devices, the DONE pins may
be connected together, as PROGRAM is a separate pin.




End of Record #149