Gregory's Serveri've added some 74-series latches to demux the address lines from the data lines. to get it to fit in a 40-pin package, the address bus is muxed with the data bus. the LEDs indicate the current address, and they count up! the program counter is counting.
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 i guess i should write a program. there is an assembler that supports this architecture (http://john.ccac.rwth-aachen.de:8000/as/) but i'll get that working later. for now i will just write it in machine code. and we have a blinking LED! this is being driven from one of the 4 flag outputs on the CPU. the bus timing looks like this. the top trace is the clock, then there is NADS, IDS (input data strobe), and finally the F11 output (which is driving the LED). i cheated and slowed the clock down for the video so you could see it blink. |
the next step is to add some program memory. it is all 16 bit, so i am using two 8 bit flash memory chips.