ADD

Purpose

perform arithmetic addition

Format

opcode add.rx, sum.mx                        2 operand

opcode addl.rx, add2.rx, sum.wx          3 operand

Operation

sum ßsum + add;                                2 operand        

sum ß add1 + add2;                           3 operand

Condition codes

N ß sum LSS 0;        

Z ß sum EQL 0;        

Vßoverflow;

C ß carry from most significant bit (integer);

C ß 0 (floating);

Exceptions

Integer overflow          

Floating overflow         

Floating underflow

Reserved operand

Opcodes

80        ADDB2           Add Byte 2 Operand   

81        ADDB3           Add Byte 3 Operand

A0       ADDW2          Add Word 2 Operand

Al         ADDW3          Add Word 3 Operand

C0       ADDL2            Add Long 2 Operand

C1       ADDL3            Add Long 3 Operand

40        ADDF2            Add Floating 2 Operand

41        ADDF3            Add Floating 3 Operand

60        ADDD2           Add Double 2 Operand

61        ADDD3           Add Double 3 Operand

Description

In 2 operand format, the addend operand is added to the sum operand and the sum operand is replaced by the result. In 3 operand format, the addend 1 operand is added to the addend 2 operand and the sum operand is replaced by the result. In floating point format, the result is rounded.

Notes

1. Integer overflow occurs if the input operands to the add have the same sign and the result has the opposite sign. On overflow, the sum operand is replaced by the low order bits of the true result.

2.         On a floating reserved operand fault, the sum operand is unaffected and the condition codes are unpredictable.

3.         On floating underflow, the sum operand is replaced by 0.

4.         On floating overflow, the sum operand is replaced by an operand of all bits 0 except for a sign bit of 1 (a reserved operand). N ß1; Z ß 0; V ß 1; and C ß 0.