Re: The ROR bug - seems it wasn't a bug after all.

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Mon, 12 Feb 2024 16:34:09 +0100 Message-ID: <616d5761-3810-4fe6-b2b6-dd4a4e2882d8_at_laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 2/12/24 15:27, A. Fachat wrote:
> 
> Am 12.02.24 um 11:25 schrieb didier derny:
>> Frankly I don't know why it's a bug or not
>> The essential is that finally they made a great processor that powered
>> our machines...
>>
>> I am more concerned by the w65c51 and the w65c816 still sold knowing
>> that the w65c51 is unusable and the w65c816 crippled by bugs In
>> emulation mode
>>
> I know the 6551 has ... problems ...

With the 6551 it depends on the version... The NMOS 6551 has a problem 
with /CTS turning off the transmitter immediately, even if that's in the 
middle of a byte being sent. It's documented in the data sheet.

On the w65C51 the transmitter empty bit doesn't work.

I think the old 65C51 did work properly, but was a bit limited with the 
baud rates.

I'd try to hook up a 16550 to a 6502 if I needed a UART for a new design.

  Gerrit