I have read a lot about this rather strange microprocessor but I have not (yet) used it myself. I have a number of them in the webshop and if I have time and a nice project I will definitely do something with them. But why is this processor so weird? When the processor came out it was a very fast processor (6.4 MHz) but the processor did need 10 Volt power supply. Later versions no longer had these limitations. The chip had sixteen 16-bit registers that could also be used as thirty-two 8-bit registers and an accumulator register D.
It had a limited form of DMA and any register could be used (selected) as a PC (program counter). All instructions were 8 bit, 4 bit opcode and 4 bit operand. The processor had no real conditional branching (some form of conditional skips), had no subroutine support, and no real stack, but with some clever use of registers this could be programmed around.
There are a number of microcomputers based on the 1802, including the COSMAC ELF (1976), Netronics ELF II, Quest Super ELF, COSMAC VIP, Comx-35. The processor is still (limited) available and there are still a number of enthusiastic hobbyists who build and develop new devices with it. At the bottom of the page is an overview of 1802 projects.
Links RCA 1802
- Wikipedia page about the RCA1802 – https://en.wikipedia.org/wiki/RCA_1802
- Page about the RCA1802 with a lot of documentation – http://www.decodesystems.com/cosmac/#cdp1802
- The 1802 Membership Card project – http://www.sunrise-ev.com/1802.htm
- Information about the 1802 Cosmicos computer – http://retro.hansotten.nl/radio-bulletin/1802-cosmicos/
- Nice page about the RCA 1802 – https://academickids.com/encyclopedia/index.php/RCA_1802
- Datasheet of the RCA 1802 processor – https://www.heinpragt.com/download1/CDP1802ACE_datasheet.pdf
