Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

161

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

Signed Saturate and Unsigned Saturate to any bit position, with optional shift before saturating.
Syntax

op{cond} Rd, #n, Rm {, shift #s}

where:
opis one of:
SSAT Saturates a signed value to a signed range.
USAT Saturates a signed value to an unsigned range.
condis an optional condition code, see 

.

Rdis the destination register.
nspecifies the bit position to saturate to:
n ranges from 1n ranges from 0 to 31 for USAT.
to 32 for SSAT
Rmis the register containing the value to saturate.
shift #sis an optional shift applied to Rm before saturating. It must be one of the

following:
ASR #swhere s is in the range 1 to 31.
LSL #s

where s is in the range 0 to 31.

Operation
These instructions saturate to a signed or unsigned n-bit value. 
The SSAT instruction applies the specified shift, then saturates to the signed range

-2

–1

≤ x ≤ 2

–1

-1.

The USAT instruction applies the specified shift, then saturates to the unsigned range 0 ≤ x ≤ 2

-1.

Restrictions
Do not use SP and do not use PC

Condition Flags
These instructions do not affect the condition code flags.
If saturation occurs, these instructions set the Q flag to 1.
Examples

SSAT

R7, #16, R7, LSL #4

; Logical shift left value in R7 by 4, then 

; saturate it as a signed 16-bit value and

; write it back to R7

USATNE

R0, #7, R5

; Conditionally saturate value in R5 as an 

; unsigned 7 bit value and write it to R0.