CS21 Project - Part B

This is a repository for CS21 - Part B

Opcode Decomposition

Type	Opcode	Func 3	1st Bit Function	2nd Bit Function	3rd Bit Function
A	00000	000 - 011	1st bit specifies the ALU Operation	2nd bit is used for ALUSrcA (ACC or CF:ACC)	3rd bit is ignored
B	00000	100 - 111	1st bit specifices RegWrite, ~(1st bit) specifices MemWrite	2nd bit specifies desired MemAdd	3rd bit is ignored
C	00001	000 - 011	1st bit specifies ALUSrcA (Either ACC or CF + ACC)	2nd bit specifies ALUOp (+ or -)	3rd bit is ignored (thus far, I haven't debugged this one yet)

ALU Modes

1. 0000 is for rotation to the left
2. 0001 is for rotation to the right
   • There should probably be some trigger here so that the overflow bit can be outputted
3. 0010 is for addition
4. 0011 is for subtraction
5. 0100 is for AND
6. 0101 is for OR
7. 0110 is for XOR
8. 0111 is for rotation to the left WITH CF bit
9. 1000 is for rotation to the right WITH CF bit

ResultSrc Modes

1. 00 is for the ALU output
2. 01 is for data-from-memory output

AddSrc Modes

1. 0 is for RB:RA
2. 1 is for RD:RC

ALUSrcA Modes

1. 00 should be for the currently-read register at ACC
2. 01 should be for Mem[MemAdd]
3. 10 should be for CF + ACC (again, precompute this)

ALUSrcB Modes

1. 00 is for Mem[MemAdd]
2. 01 is for the immediate that is entered

CFSrc Modes

This is not implemented, but here's the idea:

1. 00 is for fixed zero
2. 01 is for fixed one.
3. 10 is for the overflow / underflow bit from an ALU operation
4. 11 is for the NBit that happens during a rotate ALU operation