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2 Modules working independently but not together on FPGA

Started by Unknown March 6, 2009
Hi,

I have 2 modules ( 1 UART and another module used to test external
SRAMs ).

Every single module is working prefectly when alone on the Spartan 3
borad.

when i put them together, the UART doesn't work anymore. i have the
clock excessive skew problem, and i'm pretty sure it comes from there.
The RX module is working perfectly while the TX module is not working.

the UART provides in its output a 274 bit signal that serves as an
input to the second module. i'm using the same clock for both modules.
and that's the only/ common interaction signals i am using.

When i don't use the shift register as an input for the second module,
and i just use zeros instead, the Tx works !! so i thought it comes
from placement/ routing ...


Any idea, suggestion will be much appreciated.

Best regards,

Hassen.
On Mar 6, 5:53=A0am, hassen.kar...@gmail.com wrote:
> Hi, > > when i put them together, the UART doesn't work anymore. i have the > clock excessive skew problem, and i'm pretty sure it comes from there.
Not sure what the "clock excessive skew problem" is, but it certainly doesn't sound right...fix it.
> > Any idea, suggestion will be much appreciated. >
1. Simulation. Create a testbench, exercise the design and make sure that it is doing exactly what you expect under as many conditions as you can come up with that model how you intend to use the design. 2. Static timing analysis. Make sure the analysis is checking clock domain transfers, specify the setup time, hold time that the PCBA can deliver for all inputs, specify the clock to output and propagation delay that the PCBA requires for all outputs. Verify that the timing analysis reports shows that all timing requirements have been met. 3. Verify pinouts match what the PCBA is expecting. 4. Do not waste your time using the actual Spartan 3 board until steps 1,2 and 3 have been completed successfully. Kevin Jennings