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From: bknpk@h...<bknpk@h...>
Date: Sat Feb 19 08:10:24 CET 2005
Subject: [usb] next_RXSameBitCount code bug
I thinkd that the file processRxBit.v contains a logical error at 424.

In the case of CurrState_prRxBit during `DATA_RX_CHK_SE0: the
counter next_RXSameBitCount should be cleared and not loaded with
one.
My suggested fix is under //by PK bknpk@h...

`DATA_RX_CHK_SE0:
begin
next_bitStuffError <= 1'b0;
if (RxBits == `SE0)
begin
NextState_prRxBit <= `DATA_RX_WAIT_PRB_RDY;
end //RxBits == `SE0
else
begin
NextState_prRxBit <= `DATA_RX_DATA_DESTUFF;
if (RxBits == oldRXBits) //NRZI no change 1 /change 0
//if the current 'RxBits' are the same as the old 'RxBits', then
begin
next_RXSameBitCount <= RXSameBitCount + 1'b1;
//inc 'RXSameBitCount'
if (RXSameBitCount == `MAX_CONSEC_SAME_BITS)
//if 'RXSameBitCount' == 7 there has been a bit stuff error
next_bitStuffError <= 1'b1;
//flag 'bitStuffError'
else //else no bit stuffing error
begin
next_RXBitCount <= RXBitCount + 1'b1;
if (RXBitCount != 4'h7) begin
next_processRxBitRdy <= 1'b1;
//early indication of ready
end
next_RXByte <= { 1'b1, RXByte[7:1]};
//RZ bit <= 1 (ie no change in 'RxBits')
end
end
else //else current 'RxBits' are
different from old 'RxBits'
begin
if (RXSameBitCount != `MAX_CONSEC_SAME_BITS)
//if this is not the RZ 0 bit after 6 consecutive RZ 1s, then
begin
next_RXBitCount <= RXBitCount + 1'b1;
if (RXBitCount != 4'h7) begin
next_processRxBitRdy <= 1'b1;
//early indication of ready
end
next_RXByte <= {1'b0, RXByte[7:1]};
//RZ bit <= 0 (ie current'RxBits' is different than old 'RxBits')
end
//by PK bknpk@h...
//next_RXSameBitCount <= 4'h1;
next_RXSameBitCount <= 4'h0;
//reset 'RXSameBitCount'
end
next_oldRXBits <= RxBits;
end
end