ADD Instruction

Purpose:

To perform arithmetic addition

Format:

opcode add.rx, sum.mx
opcode add1.rx, add2.rx, sum.wx

Operation:

sum <- sum + add;
sum <- add1 + add2;

Condition
Codes:

N <- sum LSS 0;
Z <- sum EQL 0;
V <- overflow;
C <- {carry from the most significant bit} (Integer);
C <- 0 (Floating);

Exceptions:

Integer Overflow;
Floating Overflow;
Floating Underflow;
Reserved Operand (Float)

Opcodes:

80	ADDB2	Add Byte 2 Operand
81	ADDB3	Add Byte 3 Operand
A0	ADDW2	Add Word 3 Operand
A1	ADDW3	Add Word 2 Operand
C0	ADDL2	Add Long 2 Operand
C1	ADDL3	Add Long 3 Operand
40	ADDF2	Add Float 2 Operand
41	ADDF3	Add Float 3 Operand
60	ADDD2	Add Double 2 Operand
61	ADDD3	Add Double 3 Operand

Description:

In the 2 operand format, the addend operand is added to the sum operand and the sum operand is replaced with the result. The addend operand is unaffected.

In the 3 Operand format, the addend 1 and addend 2 operands are added together and the sum operand is replaced with the result.The addend operands are unaffected.

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 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 is replaced by an operand of all 0 bits except for the sign bit of 1 (a reserved operand (-1)). N <- 1; Z <- 0; V <- 1; and C <- 0.