I recently built a prototype using a xilinx spartan-iie specifically the xc2s150e-fgg456 which is programmed with an xcf02s prom. I have the prom connected first in the jtag chain. I am unable to detect the fpga. If i "tap" the tdo of the prom i can detect and program it fine, but the tdo of the fpga is always floating. I found an error in my design where the program pin, which is connected to the cf pin on the prom, is pulled high with a 4k7 resistor. I have tried pulling it low to no avail. I am able to access the tdo solderball from the side, so i know it is not a bad connection. Also, while programming the prom, the fpga seems to randomly pull outputs high/low about once every second. I'm not sure how this is possible, but it would indicate to me that the data stream is able to cause a reset of the chip. Does anyone know how i can get further information on the problem, or have any ideas what the problem could be? Thanks in advance for any help.
- posted
16 years ago