Message-ID: <140@qumix.UUCP>
Date: Fri, 26-Oct-84 04:23:18 EST
Article-I.D.: qumix.140
Posted: Fri Oct 26 04:23:18 1984
Date-Received: Sun, 28-Oct-84 04:41:10 EST
Distribution: net
Organization: Qume Corp., San Jose, CA
Lines: 44


 
Subject: vicmodem to rs422 conversion


I just got this working!!!   It only cost me $1.60 for the 9 pin
connector since I already had the $59 vicmodem and scrap parts.
Some will scoff but this is a poor man's modem for the Macintosh.  A
bit slow (300 bps) but when the wife watches the budget you have to
start somewhere.  I also have a home-brew auto dial circuit but I
haven't converted that from the vic to mac yet.


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


   MAC   function       breadboard          VICMODEM     function

   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 /
			   --------
			 
The MAC book (red cover) seems to say you can run the rs422 lines open
ended like this.  They talk about doing it with the imagewriter.