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seblovett / VLSI

VLSI design project
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ISA Changes #45

Closed mw92 closed 10 years ago

mw92 commented 10 years ago

Just so everyone is aware, there is an alternative set of opcodes I am working on atm which would appear to better minimise the amount of logic involved in decoding in the ALU. (saves about 13 cells compared to previous).

Also, does anyone have any idea how to bit slice the LLI function? Currently im having to implement it unsliced.

I shall upload amended ISA tomorrow.

seblovett commented 10 years ago

How have you done LUI?

Also, what's happening with the SP? I thought we were getting rid, but your I/S still has SP in it?

mw92 commented 10 years ago

LUI is just an fixed 8 bit shift which takes in the 'B' input to be shifted. PUSH/POP have been left in for now since it may be useful, SP should have been replaced with R7

mw92 commented 10 years ago

Just written a draft for multiply program, PUSH/POP are beneficial

seblovett commented 10 years ago

Why has LDW been assigned OpCode 0000? What about NOP? Else things will happen if it is reading blank memory...

mw92 commented 10 years ago

It better grouped with other addition-type functions for smaller ALUDecoder, NOP isnt strictly part of instruction set but is included as 11000. Programs written will have a tight loop at end if it doesnt go back to start, this prevents reading uninitialised memory.

mw92 commented 10 years ago

new set adopted