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 118

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

Signed Subtract 16 and Signed Subtract 8

Syntax

op{cond}{Rd,} Rn, Rm

where:

op

is any of:

SSUB16 Performs two 16-bit signed integer subtractions.

SSUB8 Performs four 8-bit signed integer subtractions.

cond

Rd

is the destination register.

Rn

is the first operand register.

Rm

is the second operand register.

Operation

Use these instructions to change endianness of data:

The SSUB16 instruction: 

1.

Subtracts each halfword from the second operand from the corresponding halfword of the first operand

2.

Writes the difference result of two signed halfwords in the corresponding halfword of the destination register.

The SSUB8 instruction: 

1.

Subtracts each byte of the second operand from the corresponding byte of the first operand

2.

Writes the difference result of four signed bytes in the corresponding byte of the destination register.

Restrictions

Do not use SP and do not use PC

Condition Flags

These instructions do not change the flags.

Examples

SSUB16 R1, R0     ; Subtracts halfwords in R0 from corresponding halfword

                  ; of R1 and writes to corresponding halfword of R1

SSUB8  R4, R0, R5 ; Subtracts bytes of R5 from corresponding byte in 

                  ; R0, and writes to corresponding byte of R4.