I have desingned a board with an Atmega128 and Spartan3, such that the Atmega128 configures the FPGA via the slave serial method.
In my current rev, the Atmega128 is powered by a 5V supply. The FPGA power supply is correct. The HSWAP_EN is tied low to ground. An general I/O on the microcontroller is tied to the FPGA pins.
Anyways, the problem I am having is that I am not able to pull PROG_B low to reset the FPGA. The miroprocessor pin goes low but it is not able to pull the PROG_B low at all?
The way I test this, is I have a JTAG port which I used to program the FPGA. After configruation the DONE signal goes high. So my understanding was that if I pull the PROG_B low from the microprocessor, I should be able to manually reset the FPGA and the DONE signal should go low.
I need to solve this problem before I move on to the actual programming of the board using the CCLK and DIN signals, to which I will have attach series resistors because of the Atmega128 (5V) and FPGA(3.3V).
Any suggestions or ideas appreciated.
Thanks