Commodore to Mac null modem connection.

[Info-Mac]

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From: [email protected] (Leonard Labar)
Newsgroups: net.micro,net.micro.apple,fa.info-mac
Subject: Commodore to Mac null modem connection.
Message-ID:
Date: Sun, 25-Nov-84 20:03:38 EST
Article-I.D.: qumix.171
Posted: Sun Nov 25 20:03:38 1984
Date-Received: Tue, 27-Nov-84 03:43:11 EST
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Organization: Qume Corp., San Jose, CA
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Subject: Commodore to Mac Null modem cable

The first chart below works for connecting a Mac to a Vicmodem. The
second chart is a null modem cable for connecting a Mac to a Vic20 or
C64. I just got it working. What this does is (1) saves me $471 since
I already have a dot matrix printer connected to my Vic (2) saves me
$1600 since I can use the Vic to debug Mac SW without buying a 2nd Mac.

-----RS422 (+5 volts line driver/receiver)------


MAC function breadboard VICMODEM function
(conn. 1)

1 ground ground 1, A ground

2 +5v pwr to ic -----

4 TXD+ --> 3.3k pullup --> M data to modem

5 TXD- ---- ----

6 filtered +12v ---- 10 modem power

7 carrier detect B,C (RXD)
C <-- RXD M (TXD)
H to GND carrier detect H to GND

So now I can type on the CBM keyboard and everything appears on the Mac