
SAM4CM Series [DATASHEET]
Atmel-11203C-ATARM-SAM4CM32-SAM4CM16-SAM4CM8-Datasheet_06-Oct-14
148
X
and
Y
specifies which half of the source registers
Rn
and
Rm
are used as the
first and second multiply operand.
If
X
is
B
, then the bottom halfword, bits [15:0], of
Rn
is used.
If
X
is
T
, then the top halfword, bits [31:16], of
Rn
is used.
If Y
is
B
, then the bottom halfword, bits [15:0], of
Rm
is used.
If
Y
is
T
, then the top halfword, bits [31:16], of
Rm
is used
SMLAW Signed Multiply Accumulate (word by halfword).
Y
specifies which half of the source register
Rm
is used as the second multiply
operand.
If
Y
is T, then the top halfword, bits [31:16] of
Rm
is used.
If
Y
is B, then the bottom halfword, bits [15:0] of
Rm
is used.
cond
is an optional condition code, see
“Conditional Execution”
.
Rd
is the destination register. If
Rd
is omitted, the destination register is
Rn
.
Rn, Rm
are registers holding the values to be multiplied.
Ra
is a register holding the value to be added or subtracted from.
Operation
The SMALBB, SMLABT, SMLATB, SMLATT instructions:
Multiplies the specified signed halfword, top or bottom, values from
Rn
and
Rm
.
Adds the value in
Ra
to the resulting 32-bit product.
Writes the result of the multiplication and addition in
Rd
.
The non-specified halfwords of the source registers are ignored.
The SMLAWB and SMLAWT instructions:
Multiply the 32-bit signed values in
Rn
with:
The top signed halfword of
Rm
,
T
instruction suffix.
The bottom signed halfword of
Rm
,
B
instruction suffix.
Add the 32-bit signed value in
Ra
to the top 32 bits of the 48-bit product
Writes the result of the multiplication and addition in
Rd
.
The bottom 16 bits of the 48-bit product are ignored.
If overflow occurs during the addition of the accumulate value, the instruction sets the Q flag in the APSR. No
overflow can occur during the multiplication.
Restrictions
In these instructions, do not use SP and do not use PC.
Condition Flags
If an overflow is detected, the
Q
flag is set.
Examples
SMLABB R5, R6, R4, R1
; Multiplies bottom halfwords of R6 and R4, adds
; R1 and writes to R5
; Multiplies top halfword of R6 with bottom halfword
; of R4, adds R1 and writes to R5
; Multiplies top halfwords of R6 and R4, adds
; R1 and writes the sum to R5
; Multiplies bottom halfword of R6 with top halfword
; of R4, adds R1 and writes to R5
; Multiplies bottom halfword of R4 with top halfword of
; R3, adds R2 and writes to R4
SMLATB R5, R6, R4, R1
SMLATT R5, R6, R4, R1
SMLABT R5, R6, R4, R1
SMLABT R4, R3, R2