Using C64/C128 as a Terminal on PC platform


It is possible to use your PC from another computer via a terminal program. For example, you can plug the cable described below inbetween your C64 and PC, load Novaterm to your C64, boot your PC and make use of the M$-DOS from your old-friend C64.

Today, Commodore community is lacking in modern software. We don't have popular compilers, we don't have popular archiving programs and such, in short we don't have satisfying productivity tools. But this case should not be a limiting case for us. We could use other platforms until we have the required software. For instance, if you downloaded a file which is packed by pkzip2.04, you don't have the software to depack it in your CBM environment. But, with the method described below, you can transfer this file to your PC, de-pack it there and transfer its contents back to your CBM drive without leaving your terminal program. Or as an other scenerio, you can first develop your fortran programs in your PC, check it there and then transfer them to the supercomputer of your university to execute. Even you can use your C64, while transfering data at the background with LUnix (well not yet!).

I hope above comments will encourage you to un-dust your C64 again. All you need to do is building the cable below, plugging it to your rs232 interface of C64 and one of the serial ports of your PC, and making a boot disk to use this configuration. It's really simple. By the way, if you don't have a RS232 interface, I have a very simple & cheap schematics for it. Just ask by e-mail or get it from my homepage.

If you don't have a PC I assure you that, a 286 PC and an 1.44 FD will not cost more than 30$ . You don't need a screen card, keyboard and such. Only the machine itself, an I/O card and a storage device.

Now, we will make the boot disk first:

Boot disk:

Assuming that you don't have hard-disk, or don't want to change its config.

  1. Using a complete PC, and an empty diskette in drive A:, in DOS type:

sys a:

2. Wait the command to be completed. This will transfer the system files into the diskette and make it bootable.

3. Using an editor program, prepare a config.sys file:

invoke the editor: edit a:config.sys

write these:

files=30
buffer=20,4

then save this file.

4. Using the editor again, prepare an autoexec.bat file:

run the editor program by: edit a:autoexec.bat

enter these lines (assuming you only have 640K):

prompt=$p$g
smartdrv a 128
doskey
path=a:\;
mode com1: 24,n,8,1
ctty com1
echo hello world

save this file and exit.

5. By issuing a 'dir a:' command, make sure that you have the files: 'command.com', 'config.sys', and 'autoexec.bat'.

6. Now copy the necassary files to your boot disk assuming you have a directory of 'c:\dos':

copy c:\dos\smartdrv.exe a:
copy c:\dos\doskey.com a:
copy c:\dos\mode.com a:

From now on your boot disk is ready for using the PC from COM-1 port at 2400 bps, no parity, 8 data bits and 1 stop bit. You can change 'com1' to 'com2' in the commands to use second serial port, and you can change '24' to '30' for 300bps, '12' for 1200bps, '48' for 4800bps, and '96' for 9600bps etc...

7. For X/Y/Z-Modem transfer programs, you can download one of the shareware freeware programs from the Simtel msdos archive. For example dsz??.zip pack is one of the good shareware packs. Also there is software for Punter protocol. After the installation (unzipping :) of modem data-transfer package, your PC and C64 can transfer data with the cable below.

If you can't find the files, or can't make them run. Please make me know, that I give you the exact ftp addresses of them, or give you the instructions to use them.

8. There are plenty of software which you can use with this setup. You can download and install them.

9. If you want to use your PC-keyboard with this setup. Type these:

mode lpt1=com1
type con > com1

With the first command, printscreen key sends the text screen (different from the terminal screen) to the terminal. With the second command, what you type to your PC keyboard is sent to your CBM after pressing the enter key. Control-break key will quit.

Your boot disk is ready now I hope. Please inform me about any difficulty you've faced with.

Here is the schematics for the cable. I include two types of connection. One of them is cheaper than the other.

1st type:

part list:

. 3-wired shielded cable (less than 15 meters) . two DB-25 connectors. (or two DB-9 connectors) Female type. . some connection wires.

     DB-25   to   DB-25                   DB-9   to   DB-9
     =====        =====                  =====        =====
       2------------3                      3------------2
       3------------2                      2------------3
       7------------7                      5------------5
     4-5-8        4-5-8                  7-8-1        7-8-1
     6--20        6--20                   6-4          6-4

*4,5,8 are connected to              *7,8,1 are connected to 
each other for each DB-25            each other for each DB-9 
connector.                           connector.
*6,20 are connected to               *6,4 are connected to 
each other for each DB-25            each other for each DB-9 
connector.                           connector.

2nd type: (use this one for 9600bps and higher with rts/cts flow control)

part list:

. 5-wired shielded cable (less than 15meters) . two DB25 connectors ( or two DB9 connectors) Female type. . some wires

     DB-25   to   DB-25                   DB-9   to   DB-9
     =====        =====                  =====        =====
       2------------3                      3------------2
       3------------2                      2------------3
      8-4-----------5                     1-7-----------8
       5-----------4-8                     8-----------7-1
       7------------7                      5------------5
     6--20        6--20                   6-4          6-4

*8,4 are connected to                *7,1 are connected to 
each other for each DB-25            each other for each DB-9 
connector.                           connector.
*6,20 are connected to               *6,4 are connected to 
each other for each DB-25            each other for each DB-9 
connector.                           connector.

Note that, the numbers of the pins are written on the connector.

To use both modem and this cable, you need to find or build a connector, which accepts two serial connection and directs them to your interface. That is:

DB9-male DB9-male DB9-female


       1------------1-----------1
       2------------2-----------2
       .            .           .
       .        all wires       .        
       .            .           .
       9------------9-----------9

Or with DB25 connectors, if you built DB25 type cables.

With this interface-connector, you can plug modem's cable to one of the DB-male connectors, PC-cable to other DB-male connector, and DB-female connector to your RS232 interface's DB-male connector.

If you open only one of the devices (PC or modem) at a time, there will not be a data collision.

This information is enough I guess. Please send me e-mail about your questions and/or troubles with this document.

Ilker Ficicilar
ilkerf@geocities.com
filker@newton.physics.metu.edu.tr
c068214@metu.edu.tr
http://members.tripod.com/~ilkerf/cbm.html

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