len@qumix.UUCP (Leonard Labar) (10/29/84)
Subject: Commodore to Mac Null modem cable
I recently posted the interface below to the net. It works. Since
then I've added a second cable that after unplugging the modem allows
one to interface direct from the Commodore to the Mac. Its'
description is listed below the first.
-----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<- LS04-6 5 to <- H carrier detect
8 RXD+ ---- -----
9 RXD- <-- LS04-4 &1k res., 3 to <-- C data from modem
back of mac
-------------
\ 5 4 3 2 1 /
\ 9 8 7 6 /
--------
conn. 1 signal conn. 2 (to CBM)
1,A GND 1,A
M TXD --> 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
screen that I type. Big deal! Only problem is it doesn't work the
other direction. I'm sure I don't have any faulty connections.
Q. Anybody know the answer to the above problem?
Q2. Is there a way for the Mac to receive and store M-Basic files via
the modem port? I have a lot of files without peeks and pokes that I
could use if I can do this.