Clock signal remains HIGH forever in Spartan-3 Starter Kit from Digilent

[Javi]

Hi,

I have a problem with my Spartan-3 Starter Board from Digilent (FPGA
xc3s400-5ft256). The clock (at pin T9) is always HIGH so the
combinational logic works well but obviously the sequential logic
doesn't work (flip-flops don't transition).

The first thing I did when I bought the board was check it with s3demo
and it worked fine, but later (I didn't change anything), after the
first programing clycles the problem arose.

The oscillator on the board (50MHz) works well, I think the problem is
in the FPGA itself or with de tools (I use ISE 8.1i without Service
Packs). Any idea?

Sorry for my poor english.

Thanks,
Javi

 

[Thomas Stanka]

The oscillator on the board (50MHz) works well, I think the problem is
in the FPGA itself or with de tools (I use ISE 8.1i without Service
Packs). Any idea?

Check the pinout. Maybe your driving the pin as an output.

bye Thomas

 

[Javi]

Thanks Thomas.

This is the reason. If use an IBUF component from Unisim Library
(Xilinx) everithing works well (T9 pin is a input pin, not an output),
but I never had the need to use this element before. Why now?

Javi