Null-Modem Cable Schematics

 To transfer data/prg/etc... , one can make use of the null-modem cable. With
this you don't need any modem also. Only thing has to be done is,plugging this
cable to the computers (just two computers, one to many communication with this
kind of schematics causes data collision).
 After plugging, and loading terminal programs to the computers, just send the
program, from one of the machine and receive it using the other one.


. You can use Novaterm9.5 at C64 side and Lynx at the IBM side for example.

. You have to use same transfer protocol at both sides (eg. xmodem )

. If you want you can put one of the terminal programs into BBS mode.



The Schematics:
---------------

1.)  DB-25 to DB-25 Null-Modem cable.

   db-25       db-25           Parts List
   -----       -----           ----------
tx   2-----------3 rx          . Two DB-25 male connector.
rx   3-----------2 tx          . 1-2 meter of 5(or 3) line shielded wire.
rts  4-----------5 cts *
cts  5-----------4 rts *       * If you want, you don't use rts/cts lines.
gnd  7-----------7 gnd

2.) DB-9 to DB-25 Null-Modem cable.

   db-9        db-25           Parts List
   -----       -----           ----------
rx   2-----------2 tx          . One DB-25, one DB-9 male connector.
tx   3-----------3 rx          . 1-2 meter shielded wire with 5 or 3 lines.
gnd  5-----------7 gnd
cts  7-----------4 rts *       * It is OK if not to use these lines.
rts  8-----------5 cts *

3.) DB-9 to DB-9 Null-Modem cable.

   db-9        db-9            Parts List
   -----       -----           ----------
rx   2-----------3 tx          . Two DB-9 male connector.
tx   3-----------2 rx          . 1-2 meter of 3(or 5) line shielded wire.
gnd  5-----------5 gnd
cts  7-----------8 rts *       * Not using these lines does not cause a
rts  8-----------7 cts *         problem at low speeds. Term. progs. can use
                                 XON/XOFF bytes for data flow control.


 The DB-25 Connector.   (looking at back)   The DB-9 Connector.

 13 12 ..... 3 2 1                              5 4 3 2 1
-------     --------                          -------------
\ o o o ...  o o o /                          \ o o o o o /
 \ o o  ...   o o /                            \ o o o o /
  ---- ..... -----                              ---------
  25            14                               9 8 7 6



Ilker Ficicilar
filker@newton.physics.metu.edu.tr
e068214@narwhal.cc.metu.edu.tr