For use with our Simulant C128-User Port to RS232 Adaptor follow these steps:
1. Plug in the Retro Wifi SI, USB Power & User Port Adaptor. Load Striketerm.
2. Set the Modem type to “User Port” & Baud rate to “1200”.
3. At Terminal screen carefully type (blindly if output is garbled): ATS56=1 Return
ATS48=1 Return ATS50=1 Return (Output should say “OK” & text will no longer look garbled).
4. Type ATS46=3 Return (Steps 3 & 4 are to fix garbled carrier text & RTS/CTS flow control).
5. Once these commands are all typed output should say “OK”. Repeat all commands if not.
6. Type AT&W Return (Saves your changes. Next follow normal Quick Setup instructions).

For use with our Simulant C64-UP9600 to RS232 Adaptor follow these steps:
1. First complete the steps above for Simulant C128-User Port to RS232 Adaptor.
2. Unplug Wifi modem USB power cable connected to Retro Wifi SI modem.
3. In Striketerm set Modem type to “UP9600”.
4. Set Baud rate in Striketerm to “1200” & go to Terminal screen.

5. Now plug in USB power. Type ATB4800 Return & set Striketerm baud to “4800” to match.
Always enable Striketerm “UP9600” mode with Wifi modem unpowered first.
C64 UP9600 can achieve 9600 baud but we recommend using 4800 for more reliability.

This Commodore 64 and/or Commodore 128 adaptor enables connection of our Retro Wifi SI or other 9 Pin rs232 serial devices to your C64/C128 User Port (such as linking to PC serial or null modem cables etc).

Commodore 64s and Commodore 128s don't actually have a "standard" serial rs232 port (despite having a port labelled Serial on the back!) so the Simulant C64/C128 User Port to rs232 serial adaptor adds that extra port and functionality to your C64 or C128. This enables serial devices or connections to your Commodore computer.


  • 3D Printed recyclable plastic, comes as standard in Grey but also available in black/white (see photos - choose colour when adding to cart).
  • Powered internally by the Commodore's User Port - no extra wires needed.


We offer two versions of the C64/C128 User Port to rs232 adaptor


1. Simulant C64-UP9600 to RS232 Adaptor is designed mainly for the Commodore 64 to take advantage of the UP9600 software terminal drivers (such as StrikeTerm2014 includes) that allow a faster 9600 baud speed. This adaptor does also work with C128 machines but has incompatibility with some external disk drives.

UP9600 interferes with Burst Mode on the Commodore 128. So if you choose this adaptor to allow faster speeds you won't be able to use any disk drives with the C128 that have Burst Mode, such as the 1571, 1581, or CMD drives etc. If you don't use disk drives or peripherals with Burst Mode then the UP9600 adaptor should still work fine on C128 computers.


2. Simulant C128-User Port to RS232 Adaptor works with both Commodore 64 and Commodore 128 computers at the standard User Port rate speed of up-to 2400 baud. 2400 baud was the default baud rate or speed that Commodore 64s and 128s were designed to use serial communications at.


WE OFFER A DISCOUNT ON THIS PRODUCT WHEN PURCHASED BUNDLED WITH OUR RETRO WIFI SI MODEM - CLICK HERE TO ORDER WITH THE RETRO WIFI MODEM


Please note that each unit is tested before it is shipped. We cannot offer returns, exchanges or any warranty once opened or used. This is due to this product being designed for use with old computers and vintage hardware that may be already faulty, in such rare cases this could cause problems with this device or render it defective.

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Commodore 64 / Commodore 128 User Port to rs232 Adaptor - C64 C128 to 9 Pin Serial

  • Product Code: c64-c128-user-port-to-rs232-serial
  • Availability: In Stock
  • £14.99


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Tags: c64, c128