Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 119

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

Signed Add and Subtract with Exchange and Signed Subtract and Add with Exchange.

Syntax

op{cond} {Rd}, Rm, Rn

where:

op

is any of:

SASX Signed Add and Subtract with Exchange.

SSAX Signed Subtract and Add with Exchange.

cond

Rd

is the destination register.

Rn, Rm

are registers holding the first and second operands.

Operation

The SASX instruction:

1.

Adds the signed top halfword of the first operand with the signed bottom halfword of the second operand.

2.

Writes the signed result of the addition to the top halfword of the destination register.

3.

Subtracts the signed bottom halfword of the second operand from the top signed highword of the first operand.

4.

Writes the signed result of the subtraction to the bottom halfword of the destination register.

The SSAX instruction:

1.

Subtracts the signed bottom halfword of the second operand from the top signed highword of the first operand.

2.

Writes the signed result of the addition to the bottom halfword of the destination register.

3.

Adds the signed top halfword of the first operand with the signed bottom halfword of the second operand.

4.

Writes the signed result of the subtraction to the top halfword of the destination register.

Restrictions

Do not use SP and do not use PC

Condition Flags

These instructions do not affect the condition code flags.

Examples

SASX  R0, R4, R5 ; Adds top halfword of R4 to bottom halfword of R5 and 

                 ; writes to top halfword of R0

                 ; Subtracts bottom halfword of R5 from top halfword of R4

                 ; and writes to bottom halfword of R0

SSAX  R7, R3, R2 ; Subtracts top halfword of R2 from bottom halfword of R3

                 ; and writes to bottom halfword of R7

                 ; Adds top halfword of R3 with bottom halfword of R2 and

                 ; writes to top halfword of R7.