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BigDumbDinosaur
PostPosted: Sun Feb 25, 2024 8:17 pm 
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jgharston wrote:
...the BenEater uses a 6551, so the 6551 is what is used. My personal preference is the 6850.

Nothing like working with a stone axe when a chain saw is available.  :D

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jgharston
PostPosted: Sun Feb 25, 2024 8:45 pm 
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The other thread also reminded me that CTS rising cuts off a transmitted byte if one is being transmitted. At least that is "easily" fixed, as suggested in the other thread, wire the incoming CTS to DSR instead, and poll DSR in the driver instead.
Code:
SERTX:  PHA
        ; whatever TXRDY bugfix here
SERLP2: LDA ACIASTATUS
        AND #%01000000 ; Read CTS via DSR line
        BNE SERLP2
        PLA
        STA ACIADATA
        RTS
   |
TxD+---------->- TXD
   |
DSR+--<--+
   |     |
CTS+--0v +----<- CTS
   | 

Edit: Being bit 6 could even do BIT ACIASTATUS:BVS SERLP2

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GARTHWILSON
PostPosted: Sun Feb 25, 2024 9:52 pm 
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jgharston wrote:
The other thread also reminded me that CTS rising cuts off a transmitted byte if one is being transmitted.

That's true of the NMOS 6551; but AFAIK all of the CMOS ones (ie, 65c51) let the byte finish.  I address this in the 6502-oriented RS-232 primer, just over 40% of the way down the page, in the paragraph that say, in bold, regarding the NMOS one, "I consider this to be either a serious bug, or an idiotic part of the original NMOS design" (because you'll lose a byte, even if you're just pausing for the receiving end to catch up and be ready to accept more data).

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Yuri
PostPosted: Sun Feb 25, 2024 11:26 pm 
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BigDumbDinosaur wrote:
jgharston wrote:
...the BenEater uses a 6551, so the 6551 is what is used. My personal preference is the 6850.

Nothing like working with a stone axe when a chain saw is available.  :D


Yea, when Ben Eater started getting into adding the serial stuff to his 6502, I didn't wait around for him to finish. It didn't take me long to discover that the 65C51 was bugged, so I decided to find an alternative. I ultimately managed to get some 16C550Cs that did the job.

That being said I managed to find some SC26C92s in a PLCC package. I haven't had a chance to try them out yet, but I'm thinking I'll incorporate one into a 65816 design.
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