Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet

157

SAM4E [DATASHEET]

Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14

Saturating Add and Saturating Subtract, signed.

Syntax

op{cond} {Rd}, Rn, Rm

op{cond} {Rd}, Rn, Rm

where:

op

is one of:

QADD Saturating 32-bit add.

QADD8 Saturating four 8-bit integer additions.

QADD16 Saturating two 16-bit integer additions.

QSUB Saturating 32-bit subtraction.

QSUB8 Saturating four 8-bit integer subtraction.

QSUB16 Saturating two 16-bit integer subtraction.

cond

is an optional condition code, see 

.

Rd

is the destination register.

Rn, Rm

are registers holding the first and second operands.

Operation

These instructions add or subtract two, four or eight values from the first and second operands and then writes a
signed saturated value in the destination register. 

The QADD and QSUB instructions apply the specified add or subtract, and then saturate the result to the signed
range -2

n–1

≤ x ≤ 2

n–1

-1, where x is given by the number of bits applied in the instruction, 32, 16 or 8.

If the returned result is different from the value to be saturated, it is called saturation. If saturation occurs, the
QADD and QSUB instructions set the Q flag to 1 in the APSR. Otherwise, it leaves the Q flag unchanged. The 8-bit
and 16-bit QADD and QSUB instructions always leave the Q flag unchanged.

To clear the Q flag to 0, the MSR instruction must be used; see 

To read the state of the Q flag, the MRS instruction must be used; see 

.

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.