GLINK232-A01 - UART cartridge for Commodore 64/128

Submitted by GG on Sun, 05/11/2014 - 00:02
Project Status

A new version of this project is available here

glink232Both the commodore 64 and the 128 have a software UART implementation that limits the useful speed to 2400 bauds. To work around this limitation Dr. Evil Labs and later CMD produced the SwiftLink232 and turbo232 cartridges based on the 6551 ACIA chip. Both of these have been out of production for a very long time. GLINK232 is a modern replacement for the swiftlink232 allowing the commodore 64/128 to communicate at speeds up to 38400 bauds.

Similarly to the SwiftLink, the card can be configured using jumpers at either the $DE00 or $DF00 I/O address and can use either the NMI or IRQ interrupt line (most native software use NMI, but CP/M uses IRQ).
The card uses a 3.6864MHz crystal (double the standard for a 6551) to match the baud rate table of the SwifLink.

The board can be populated in 3 different configurations:

  • Minimal configuration - ideal for computer to computer file transfer (RX/TX and CTS/RTS only)
  • SwiftLink clone - full modem control (adds DTR, DCD and DSR)
  • Jim Brain's HS232 clone - adds I/O decoder to support multiple cards

    BOM Options

    Component Minimal SwifLink HS232
    C5 no stuff 1uF 1uF
    C6 no stuff 1uF 1uF
    C7 no stuff 1uF 1uF
    C8 no stuff 1uF 1uF
    C10 no stuff no stuff .1uF
    C12 no stuff .1uF .1uF
    C14 no stuff 10uF 10uF
    J4 wire wire no stuff
    R4-R11 no stuff no stuff 0 ohm (one location only)
    U3 no stuff MAX232 MAX232
    U4 no stuff no stuff 74LS138
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