Bulletin: SM6400
Vendor:   Miscellaneous Hookup
Subject:  RS-232C Adaptor For The Commodore C64/128
          Useable With Most AEA, MFJ and Kantronics TNC's

Here's a simple interface to connect a C64/128
to any of the multimode boxes on the market.

This circuit has been used between a C64 and
an AEA PK-232, and an MFJ-1270 TNC. Running
the Common Sense terminal program...........


C64/128           RS232 Adaptor            RS232C
====================================================
A&N --------------- Ground --------------- 1&7
B&C ------------- 2-7404-1 --------------- 3   RXD
  M ------------- 3-7404-4 --------------- 2   TXD
  H -------------------------------------- 8   DCD
  E -------------------------------------- 20  DTR
  K -------------------------------------- 5   CTS
  L -------------------------------------- 6   DSR

Pins B&C from the C64/128 are connected to pin 2 of the 7404 hex inverter.
Pin 1 of the 7404 is connceted to pin 3 of the RS232 DB25 connector. This
completes the receive data path from the TNC to the computer.  Pin N from
the C64/128 is connected to pin 3 of the 7404 and pin 4 from the IC is
connected to pin 2 of the RS232 connector.  This completes the transmit
data path from the computer to the TNC.

7404 is a Hex Inverter IC with where only \two sections are used.
Pin 7 is ground or VCC(-) and pin 14 is +5VDC or VCC(+) which is
obtained from the C64/128 RS232C port pin #2.....