The main state machine had an error whereby the wb_cyc and wb_stb
outputs were not assigned in the IDLE state.
This manifested itself as follows (output from telnet console):
%> writereg 1 100 0 # read to illegal address
%> readreg 1 4 # read from legal address returns NACK
%> readreg 1 4 # next read from legal address returns right data
Read data: 01234567
The bug was because the first writereg started a WB transfer from
an unexisting address, threw an error and returned to IDLE without
releasing the wb_cyc and wb_stb outputs in the process. This meant
that on the readreg command, the WB write access would still be in
progress and only on the readreg command, an error would clear the
wb_cyc and wb_stb, which released the transfer.
The error has been fixed by placing the clearing of wb_cyc and wb_stb
in the IDLE state.