Atmel SAM4S Series, Preliminary Data Sheet

Page: 137 / 1163

137
11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
11.6.6.3 SMLA and SMLAW
Signed Multiply Accumulate (halfwords).
Syntax
op{XY}{cond} Rd, Rn, Rm
op{Y}{cond} Rd, Rn, Rm, Ra
where
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.
op is one of:
SMLA Signed Multiply Accumulate Long (halfwords)
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.