Hallo allemaal,
I started to revise my TTL6502 project,
http://www.baltissen.org/newhtm/ttl6502.htm, and was thinking about to expand it a bit. One idea was having 16 bits registers. The idea looked good for weeks until the thought struck that my 8-bits ALU couldn't handle these registers
My momentary ALU is made of two cascaded FlashRAMs, each handling 4 bits of the two operands and a total access time of 140 ns. I could emulate a 3 MHz 6502. To be able to handle 16 bits I need to cascade four FRs, meaning 280 ns. and thus 1 Mhz max
Why FRs? Simple answer: the most quick and dirty method. I have thought about using 74181's but the decimal mode spoiled the fun.
Has anybody an other idea to realise the ALU?
Many thanks in advance!
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