I'm using a Spartan 3AN in a project and am wondering... if the mode pins are set to load the config bit-stream from the internal FLASH, am I still able to directly program the FPGA via JTAG for development reasons? (i.e. without having to generate a PROM file and program the bit stream to the internal FLASH device for each iteration) Or do i need to include some method in my design to set the mode pins for JTAG only?
From UG332 (v1.6) October 26, 2009:
In iMPACT 9.2i and later, you have the option to either configure the FPGA directly
through JTAG mode or to program the Internal SPI PROM and then configure through
Internal Master SPI mode.
So make sure your using a version of iMPACT later than that one otherwise it programs the internal flash then commands the FPGA to configure in master mode from the internal flash.