The PCG 6500 is a 100% compatible clone of the programmable character set generator and sound device for the CBM PET series computers. It implements all the features, including the ability to reprogram 64 of the PET characters into custom graphics, as well as support for amplified CB2 sound output.
For PETs using the MOS 6540 rom set, there is an adapter board that mounts in place of CN1 and allows easy connection to the 6540 charrom using two DIP 28pin to ribbon adapters.
Originally, there was no way to simply disable the HAL PCG 6500 once installed. Katunori Takesita discovered a simple modification that an owner had applied to his board, which consisted of disconnecting an input of a nand-gate from address 9 of the CharROM bus (by cutting a trace) and grounding it instead, effectively disabling the RAM and re-enabling the CharROM permanently. This mod is also implemented in this replica and jumper JP1 is provided for this purpose.
Bridge JP1 to permanently enable the card like it was originally.
A small SwitchMod board has been designed providing the ability to switch between the address9 signal and GND for the input of IC8D using an 74LS00, avoiding the need to route the fast address signal over a mechanical switch. This board also has the ability to connect a 3-pin common cathode dual LED (or one or two standard LEDs) to indicate the state of the board. Connect the pins E,A,+,- on the SwitchMod to the corresponding pins on the 6500 board.
A 3d printable case is available at my printables profile.
Each programmable character provided by the PCG 6500 is programmed line by line via the PETs 6522 peripheral port A (PA7-0), which is available on the user port. PA0-4 transport the actual data, PA 5-7 address the data and address latches on the PCG 6500 See the Programming chart originally taken from the PCG 6500 manual with some fixed typos.
Software using the PCG-6500 and further documents are available on their own repository: PCG-6500 Software
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
See https://creativecommons.org/licenses/by-sa/4.0/.
This work would not have been possible without the help from a bunch of amazing people from VzEkC e. V. forums and around the world. Many thanks go out to:
- AndyG - for providing images of a working board.
- Katunori Takesita - his blog about repairing an original board had important additional images and informations.