Notes on building a 8bit computer. The circuit is simulated with the great Logisim, I've also written a converter for my assembly language and a helper to write micro instructions. Implicit
Absolute \$nn
Immediate #\$nn
Indexed \$nn,a
Indexed indirect (\$nn,a)
Indirect (\$nn)
Indirect indexed (\$nn),a

• Storage

lda #\$nn
lda \$nn
lda (\$nn)
ldb #\$nn
ldb \$nn
ldb (\$nn)
sta \$nn
sta (\$nn)
stb \$nn
stb \$nn,a
stb (\$nn),a
stb (\$nn,a)
tab transfer from AX to BX
tba transfer from BX to AX

• Math

adc #\$nn AX = AX + \$nn
adc \$nn AX = AX + {\$nn}
sbc #\$nn AX = AX - \$nn
sbc \$nn AX = AX - {\$nn}
inc AX = AX + 1
dec AX = AX - 1

• Bitwise

and #\$nn AX = AX AND \$nn
and \$nn AX = AX AND {\$nn}
ora #\$nn AX = AX OR \$nn
ora \$nn AX = AX OR {\$nn}
eor #\$nn AX = AX XOR \$nn
eor \$nn AX = AX XOR {\$nn}
lsl AX logical shift left
lsr AX logical shift right
asl AX arithmetic shift left
rol AX rotate left one bit
ror AX rotate right one bit

• Branch

bpl \$nn branch on plus (N)
bmi \$nn branch on minus (N)
bcc \$nn branch on carry clear (C)
bcs \$nn branch on carry set (C)
bne \$nn branch on not equal (Z)
beq \$nn branch on equal (Z)

• Flags

sec set carry flag
clc clear carry flag

• Registers

cmp #\$nn compare \$nn to AX
cmp \$nn compare {\$nn} to AX

• Stack

pha push AX on stack
pop pop stack top to AX

• Jump