Re: mos 6551 / w65c51

From: didier_at_aida.org
Date: Wed, 18 Oct 2023 19:28:19 +0200
Message-ID: <15fcb35c-4248-4a3b-a7a5-33c6b3739293_at_aida.org>
thanks for the information, I ordered a few from Poland
but I'll have to reduce the speed of the board to 1..2 Mhz

frankly I'm mad, I think I'll have to rebuild my board
probably with a FTDI chip usb fifo...

after the other infamous bug I found in the 65c816 in emulation mode...

thanks


On 18/10/2023 17:26, Gerrit Heitsch wrote:
> On 10/18/23 15:04, laughton_at_cyg.net wrote:
>> It's my understanding that all 65C51's made by WDC are affected, but 
>> all other versions such as mos 6551 are free of the transmit flag bug.
>
> Yes, but those have other problems. The NMOS/HMOS 6551 will stop 
> transmitting the moment /CTS goes HIGH. That can be in the middle of a 
> byte being sent. This is documented in the data sheet.
>
> As far as I know, only the 65C51 (Rockwell for example) is behaving 
> one would expect.
>
>  Gerrit
>
>
>
>>
>> More on the bug on 6502.org, here:
>> http://forum.6502.org/viewtopic.php?p=26524#p26524
>>
>> -- Jeff
>>
>> On 2023-10-18 08:45, didier_at_aida.org wrote:
>>> Hi All :)
>>>
>>> I made a board with a 65c816 and a 65c51
>>> I saw on the web that apparently the w65c51 has bug on the transmit 
>>> flag ...
>>> is there a way to identify the w65c51 with or without bugs ?
>>> I checked the plus4 rom code to check how the 6551 was programmed
>>>
>>> is this bug only on the w65c51 or also on the mos 6551 ?
>>>
>>> my goal was to study how to replace a mos 6502 by a 65c816... on a
>>> commodore 8032
>>> have a board with ram + 64ext on the board and run at 1 Mhz on the I/O
>>> and faster speed while accessing the ram  (8Mhz)
>>>
>>> thanks
>>
>
>
Received on 2023-10-18 22:00:03

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