On 2006-05-31, howard parkin wrote:
> 2) The next thing I noticed is probably something missed
> out of the initial specification. For the 32 bit data input, only
> a byte is written to the PROM. The byte that is written depends
> on which one of the 4 byte enables is active. You can fix this
> by adding the code :-
>
> wire [7:0] wr_data = (write_data[7:0] & {8{write_bytes[0]}}) |
> (write_data[15:7] & {8{write_bytes[1]}}) |
> (write_data[23:16] & {8{write_bytes[2]}}) |
> (write_data[31:24] & {8{write_bytes[3]}};
Is it needed? I assumed the software could arrange so that the source
data is stored in the upper byte, independent of target address, thus
saving the multiplexer gates. (I was also woundering why not specify
the full address instead of write_bytes, but I assume that has something
to do with the PCI standard.)
Another thing. The files that I used to produce the simulation output
can be found at http://85.235.225.158/~petter/ogp/spi_prom/:
spi_prom_sim.v clipped from Tim's second post on this thread
spi_test.v clipped from Tim's same post, with a few tweaks
Makefile if you care
They may should still be applicable, unless the inferface is changed.
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