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+---- Thread: 4-bit stack based IS (/thread-2436.html)
4-bit stack based IS - MelvinS4_ - 02-15-2014
I recently found the wonderful world of stack based processor architectures. I've made a simple IS that I hope to implement in a minecraft CPU, but before that I was hoping to get some feedback from folks who are more knowledgeable than me
Without further endue, here is the IS:
Code:
0 0000 PUSH:STACK pushes first element (0 if stack is empty)
1 0001 PUSH:REG pushes from the GPR
2 0010 PUSH:RAM pushes from RAM
3 0011 PUSH:RAMA pushes from RAM address reg
4 0100 POP:STACK deletes first element
5 0101 POP:REG pops to the GPR
6 0110 POP:RAM pops to RAM
7 0111 POP:RAMA pops to RAM address reg
8 1000 JMP:C jump if carry out is on
9 1001 JMP:> jump if a > b
a 1010 JMP:< jump if a < b
b 1011 JMP:= jump if a = b
c 1100 ALU:A push A + B
d 1101 ALU:AC push A + B + 1
e 1110 ALU:N push A NAND B
f 1111 HALT halts the CPUThe things which are yet to be decided upon are:
1. if a is the GPR and b is the top of stack OR a is the top of stack and b is the second item in stack,
2. if ALU calls will simply push the result OR pop it's operands first
3. if JMP calls will jump to the value in the GPR OR in the top of the stack.
(Please note the difference in capitalization of a and A, A and B are the top and second items in the stack, while a and b have not yet been decided.)
Any feedback and suggestions are welcome!
