Thursday, August 1, 2013

COSMAC Elf Clone Built with PICs

Ted Rossin put together a modern day version of a COSMAC ELF retro computer using a PIC processor.

"The PIC is clocked with a 7.16 MHz crystal which is 4x the rate of a standard Elf with Pixie chip.  This gave me 32 PIC instructions per 1802 state cycle to get the job done.  I use the internal PLL to multiply the clock by another 4 as the PIC needs 4 clocks per instruction.  For most 1802 instructions this was cake but some were quite challenging as the PIC has to implement the instruction plus keep TPA and TPB going as well as implement the normal 1802 bus cycles not to mention the need to respond to the mode pins, DMA and interrupts."