simple cpu #17

16 x 32-bit registers
R0 : Zero Register. Reads as zero. Writes do nothing
R1 : Unit Register. Reads as one.  Writes do nothing
R2 : Program Counter  R3 : Accumulator  R4: Program Counter
R5 : Flags Register (Implementation-dependent)
R6-R15 : No special meaning
assembler   opcode       Meaning
jalc r   |  0000rrrr  |  If (Rr==0): Rr <- PC+1, PC <- Accumulator
jal  r   |  0001rrrr  |  Rr <- PC+1, PC <- Accumulator
add  r   |  0010rrrr  |  Accumulator <- Accumulator + Rr, PC <- PC+1 [ unsigned 32-bit add ]
sub  r   |  0011rrrr  |  Accumulator <- Accumulator - Rr, PC <- PC+1 [ unsigned 32-bit subtract ]
rmem r   |  0100rrrr  |  Accumulator <- Memory_Byte_At[Rr], PC <- PC+1
wmem r   |  0101rrrr  |  Memory_Byte_At[Rr] <- Accumulator, PC <- PC+1
rreg r   |  0110rrrr  |  Accumulator <- Rr, PC <- PC+1
wreg r   |  0111rrrr  |  Rr <- Accumulator, PC <- PC+1
nand r   |  1000rrrr  |  Accumulator <- NOT( Accumulator AND Rr ), PC <- PC+1
and  r   |  1001rrrr  |  Accumulator <- (Accumulator AND Rr), PC <- PC+1
or   r   |  1010rrrr  |  Accumulator <- (Accumulator OR Rr), PC <- PC+1
xor  r   |  1011rrrr  |  Accumulator <- (Accumulator XOR Rr), PC <- PC+1
pfix n   |  1100nnnn  |  Accumulator <- ( (Accumulator << 4) OR n ), PC <- PC+1
nfix n   |  1101nnnn  |  Accumulator <- ( ( (NOT Accumulator) << 4) OR n ), PC <- PC+1
rol  n   |  1110nnnn  |  Accumulator <- Accumulator ROTATED_LEFT_BY n bits, PC <- PC+1
ror  n   |  1111nnnn  |  Accumulator <- Accumulator ROTATED_RIGHT_BY n bits, PC <- PC+1