Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
121
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
12.6.5.11 SHASX and SHSAX
Signed Halving Add and Subtract with Exchange and Signed Halving Subtract and Add with Exchange.
Syntax
op{cond} {Rd}, Rn, Rm
where:
op
is any of:
SHASX Add and Subtract with Exchange and Halving.
SHSAX Subtract and Add with Exchange and Halving.
cond
is an optional condition code, see
.
Rd
is the destination register.
Rn, Rm
are registers holding the first and second operands.
Operation
The SHASX instruction:
1.
Adds the top halfword of the first operand with the bottom halfword of the second operand.
2.
Writes the halfword result of the addition to the top halfword of the destination register, shifted by one bit to
the right causing a divide by two, or halving.
the right causing a divide by two, or halving.
3.
Subtracts the top halfword of the second operand from the bottom highword of the first operand.
4.
Writes the halfword result of the division in the bottom halfword of the destination register, shifted by one bit
to the right causing a divide by two, or halving.
to the right causing a divide by two, or halving.
The SHSAX instruction:
1.
Subtracts the bottom halfword of the second operand from the top highword of the first operand.
2.
Writes the halfword result of the addition to the bottom halfword of the destination register, shifted by one bit
to the right causing a divide by two, or halving.
to the right causing a divide by two, or halving.
3.
Adds the bottom halfword of the first operand with the top halfword of the second operand.
4.
Writes the halfword result of the division in the top halfword of the destination register, shifted by one bit to
the right causing a divide by two, or halving.
the right causing a divide by two, or halving.
Restrictions
Do not use SP and do not use PC
.
Condition Flags
These instructions do not affect the condition code flags.
Examples
SHASX
R7, R4, R2 ; Adds top halfword of R4 to bottom halfword of R2
; and writes halved result to top halfword of R7
; Subtracts top halfword of R2 from bottom halfword of
; R4 and writes halved result to bottom halfword of R7
SHSAX
R0, R3, R5
; Subtracts bottom halfword of R5 from top halfword
; of R3 and writes halved result to top halfword of R0
; Adds top halfword of R5 to bottom halfword of R3 and
; writes halved result to bottom halfword of R0.