RE: userport: C64, Plus4, others?

From: Baltissen, GJPAA (Ruud) <>
Date: Wed, 7 Mar 2012 08:20:14 +0100
Message-ID: <>
Hallo Gábor, 

Jim > You do need to ensure 2 more lines besides the 8 data lines....

One of my very first projects was the ancestor of CBM-HD: the Userport was connected to the LPT port of a PC. In this case I only used 4 bits for data transfer (the same four bits as used by X1541) plus two data bits and two bits of the status port for handshake. Not the fastest way but the most surest: I had control of every bit of both systems.

Then I turned the LPT port into a bidirectional, used DATA and CLOCK of the IEC bus as handshake lines and PA2 to tell the PC whether the these last two lines were valid or not. In this case I knew that if there was an error, I only had to look in the communication part as the rest proofed to work fine with the 4-bit solution. Again, not the ideal way but I learned a lot again and it was fun!

I hope this helps a bit.

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Received on 2012-03-07 08:00:04

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