VIC-1112 IEEE-488 interface cartridge

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IEEE-488 interface cartridge
Chipitos.be-VIC-1112.jpg
cartridge
Part number VIC-1112
ROM size 2K
Start address $B000
Autostart No, SYS 45065

The IEEE-488 interface is a cartridge that was produced by Commodore to enable IEEE-488 devices to be connected to the VIC-20. The IEEE-488 bus (also known as GPIB) allows a computer to communicate and control a wide range peripherals of the time, from plotters to test equipment. Most importantly, the VIC's predecessor, the PET, had an IEEE-488 interface and a number of printers and floppy disk drives were produced for it.

At the top of the cartridge is a 0.156" edge connector which is used to connect one or more devices using a non-standard cable (Commodore part number 320101 for example). All Commodore cartridge cases have a cut-out but the VIC-1112 is the only peripheral that makes use of it.

While the VIC-1112 enabled the VIC-20 to use storage devices with a greater storage capacity and faster transfer rate the high cost of the peripherals at the time meant that few VIC-20 users owned this cartridge.


Usage

To use the cartridge connect the devices, power on the devices before the computer then enter

SYS 45065

-- IEEE-488 DRIVER --
READY.

All I/O operations (for example, PRINT#) to devices numbered 4 to 30 will now occur on the IEEE-488 bus, the internal serial bus is effectively disabled.


Modern Replica

In 2015 a Kickstarter project was launched to build a reproduction of the original VIC-1112, VIC-20 IEEE interface


Issues with ROM

Examination of the ROM disassembly shows there are large sections of dead code, suggesting it may have adapted from some other ROM. There are also a number of mistakes in the hardware initialization and the LOAD routines which could cause bugs in some circumstances.

The VIC-1112 was intended to support being automatically activated from the VIC-1212 Programmers Aid Cartridge (which in turn can be activated by the VIC-1211A Super Expander). The address used for the warm reset routine is incorrect and it appears that part of the autostart signature was then NOP'ed out. See Denial thread for more details.


Images

Links

ROM dump: Media:VIC-1112_ROM_DUMP.bin

Annotated ROM disassembly