Evaluating Arithmetic Expressions

For purposes of this page, I'm defining a "simple expression" as one that can evaluated using a single HC11 instruction, and a "complex expression" as one that requires more than one instruction.

• Simple Expressions

increment memory location or register

inc, inca, incb, ins, inx, iny

decrement memory location or register

dec, deca, decb, des, dex, dey

add to register

aba, abx, aby, adda, addb, addd, adca, adcb

HLL Code	Corresponding Assembly Code
a = a + b;	aba
x = x + b;	abx
y = y + b;	aby
a = a + value;	adda value
b = b + value;	addb value
d = d + value;	addd value
a = a + C + value;	adca value
b = b + C + value;	adca value

subtract from register

sba, suba, subb, subd

HLL Code	Corresponding Assembly Code
a = a - b;	sba
a = a - value;	suba value
b = b - value;	subb value
d = d - value;	subd value

negate

neg, nega, negb

logical

anda, andb, bset, com, coma, comb, eora, eorb, oraa, orab

condition codes

clc, clv, sec, sev

condition codes from data (remember: may other instructions also end up setting the condition codes as a side-effect).

cmp, tst, bita, bitb, cba, cmpa, cmpb, cpd, cpx, cpy

• Complicated Expressions

Add two values together

HLL Code	Corresponding Assembly Code
result = value1 + value2;	ldax value1 addx value2 stax result
x = x + b;	abx
y = y + b;	aby
a = a + value;	adda value
b = b + value;	addb value
d = d + value;	addd value
a = a + C + value;	adca value
b = b + C + value;	adca value

Binary Coded Decimal