A bit-banged full duplex serial terminal for the Commodore PET/CBM computers, including those running BASIC 1!

Written by Hayden Kroepfl (Chartreuse) 2017-2022

BASIC Save/Load and XMODEM extensions by Adam Whitney (K0FFY) 2022

PETTERM can now handle 2400 baud, along with much improved ANSI terminal compatibility.

Requires at least 8kB of RAM -- For 4kB PET's please use 0.4.0 version or prior for now

Can Load and Save BASIC programs over the serial connection using XMODEM-CRC protocol. Using the high-mem version it can be loaded on top of an existing basic program provided there is enough free space after the program. These versions don't include a stub loader and you must manually SYS xxxx into the program.

• Can work with a 40 or 80 column PETs with either the graphics or business keyboard.
• Can be loaded from tape or disk.
• Works on all versions of BASIC including the oldest PET 2001s with BASIC 1.
• Can work with as low as 8kB of RAM.
• Requires only a simple two wire serial interface.
• BASIC programs can be loaded or saved via serial using the XMODEM-CRC protocol.

• Off/Rvs key acts as a Ctrl key.
• Clr/Home opens up the PETTERM menu for changing baud rate and character set modes
• PET cursor keys work as expected
• Inst/Del is a backspace key
• Additional shifted keys to improve *nix usability:
  • Shift-@ = ~
  • Shift-' = `
  • Shift-[ = {
  • Shift-] = }
  • Shift-^ (up arrow) = |
• Run/Stop sends Ctrl-C
• Other keys can be sent by their control code:
  • Tab = Ctrl-I
  • Esc = Ctrl-[ (For Alt/Meta, send Esc then the key)
• Terminal emulates ANSI escape codes (supports all required by ansi TERMCAP/TERMINFO)
• Load/Save BASIC Program using XMODEM-CRC

Rx (to the PET) should be connected to pin C AND pin B of the user-port.

Tx (from the PET) should be connected to pin M of the user-port.

Don't forget the ground connection to either pin N or Pin 1

If coming from a version prior to 0.4.0, a connection between pin C and B of the user-port is required. Adapters meant for VIC-20 or C64 use should already have this present. This change is required for all baud rates in this version.

These connectors are designed to be compatible with standard serial adapters and modems for the VIC-20 and C64, however as the PET does not provide 5v on the userport, an inline adapter or external power is needed for these circuits, and the 5v pin on the userport connector disconnected.

Commodore PET - RS-232 simple conversion circuit:

    TTL(0V - +5V)                  RS-232 (-13V - +13V)

                5v DC Power (take from cassette or internal)
     ______       |     _________             ________
    |      |      |--- |   MAX   |           |        |
    |      |B\         |L  232  R|           |        |
    | PET  |  |--R1OUT-|O       S|--T1OUT---2| RS-232 |
    | User |C/         |G       2|--R1OUT---3| Serial |
    | Port |M----T1OUT-|I       3|           |  DB9   |
    |      |           |C       2|           |        |
    |______|1-----GND--|_________|--GND-----5|________|

Warning: Connections to the PET user port are RS-232 TTL level signals (0V to +5V). Standard RS-232 serial level signals are -13V to +13V (or more). Connecting standard RS-232 level signals to your PET's user port without an RS-232 to TTL interface will damage your computer and make you sad. (See this SparkFun explanation for more details.)

Default:

• petterm - 40 column PETs with graphics keyboard, BASIC save/load extension

All:

The original PETTERM without the BASIC save/load extension

• petterm40G - 40 column PETs with graphics keyboard (eg 2001, some 4032)
• petterm40B - 40 column PETs with business keyboard
• petterm80G - 80 column PETs with graphics keyboard
• petterm80B - 80 column PETs with business keyboard

Basic:

The higher memory versions with the BASIC save/load extension

• petterm8K_40G.prg - 40 column PETs with graphics keyboard, BASIC save/load, higher memory version (SYS 3200)
• petterm8K_80G.prg - 80 column PETs with graphics keyboard, BASIC save/load, higher memory version (SYS 3200)
• petterm8K_40B.prg - 40 column PETs with business keyboard, BASIC save/load, higher memory version (SYS 3200)
• petterm8K_80B.prg - 80 column PETs with business keyboard, BASIC save/load, higher memory version (SYS 3200)
• petterm16K_40G.prg - 40 column PETs with graphics keyboard, BASIC save/load, higher memory version (SYS 8192)
• petterm16K_80G.prg - 80 column PETs with graphics keyboard, BASIC save/load, higher memory version (SYS 8192)
• petterm16K_40B.prg - 40 column PETs with business keyboard, BASIC save/load, higher memory version (SYS 8192)
• petterm16K_80B.prg - 80 column PETs with business keyboard, BASIC save/load, higher memory version (SYS 8192)
• petterm32K_40G.prg - 40 column PETs with graphics keyboard, BASIC save/load, higher memory version (SYS 24576)
• petterm32K_80G.prg - 80 column PETs with graphics keyboard, BASIC save/load, higher memory version (SYS 24576)
• petterm32K_40B.prg - 40 column PETs with business keyboard, BASIC save/load, higher memory version (SYS 24576)
• petterm32K_80B.prg - 80 column PETs with business keyboard, BASIC save/load, higher memory version (SYS 24576)

PRG files are the native programs, can be added to a tape or disk image

TAP files are tape images