Message-ID: <148@qumix.UUCP>
Date: Mon, 29-Oct-84 00:38:33 EST
Article-I.D.: qumix.148
Posted: Mon Oct 29 00:38:33 1984
Date-Received: Sat, 3-Nov-84 03:53:19 EST
Distribution: net
Organization: Qume Corp., San Jose, CA
Lines: 53


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.