Re: userport: C64, Plus4, others?

From: Imre Széll <>
Date: Tue, 6 Mar 2012 17:28:15 +0100
Message-ID: <>
Back in the mid 90's I've built a centronics printer cable for my plus/4.
It used the 6529 for data and two pins of the ACIA for handshake (I can't
remember which two of them but I have the sources somewhere). It required
some initialization to use them as a fixed state pin but not too complex.
I used it to print to a HP laser printer.
2012.03.06. 17:21, "Gerrit Heitsch" <> ezt írta:

> On 03/05/2012 11:10 PM, Gábor Lénárt wrote:
>> Hi,
>> I prefer user port, because it exists on other machines as well, not just
>> C64. Like Plus/4. And it's my another question: it's not so clear for me:
>> has the Plus/4 some similar handshaking possibilities via its user port as
>> the C64/CIA has?
> No. The Plus/4 user port is completly different. The I/O-Bits are the
> portbits of a 6529B, one of them used to detect the button press for the
> datasette (If no tape is attached you have all 8 bits). Those are just I/O,
> no handshake other features available. You don't even have a data direction
> register. To use a bit as input, write a '1' to it before reading it.
> The Plus/4 also has a real ACIA (8551/6551A) for the RS232. You only need
> a few inverters and a MAX232 to be able to use it with a modem or a PC on
> the other side. Without modification, you can reach 19200 bps. This also
> means you cannot easily 'abuse' those I/O bits for other purposes.
>  Gerrit
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Received on 2012-03-06 17:00:35

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