Subtract Memory From Accumulator
Memonic	Mode	Opcode	Cycles	Bytes
SUBA	Immediate	80	2	2
	Direct	90	3	2
	Indexed	A0	5	2
	Extended	B0	4	3
SUBB	Immediate	C0	2	2
	Direct	D0	3	2
	Indexed	E0	5	2
	Extended	F0	4	3

A = A - M
B = B - M

Results:
H not affected
N set if bit 7 is 1
Z set if all bits are 0
V set on 2's complement overflow
C set on carry from bit 7