134
SAM4CP [DATASHEET]
43051E–ATPL–08/14
12.6.6.8 SMMUL
Signed Most Significant Word Multiply
Syntax
op{
R
}{
cond
}
Rd
,
Rn
,
Rm
where:
op
is one of:
SMMUL Signed Most Significant Word Multiply.
R
is a rounding error flag. If
R
is specified, the result is rounded instead of being truncated. In this case the
constant 0x80000000 is added to the product before the high word is extracted.
cond
is an optional condition code, see
“Conditional Execution”
.
Rd
is the destination register.
Rn, Rm
are registers holding the first and second operands.
Operation
The SMMUL instruction interprets the values from
Rn
and
Rm
as two’s complement 32-bit signed integers. The SMMUL
instruction:
Multiplies the values from
Rn
and
Rm
.
Optionally rounds the result, otherwise truncates the result.
Writes the most significant signed 32 bits of the result in
Rd
.
Restrictions
In this instruction:
do not use SP and do not use PC.
Condition Flags
This instruction does not affect the condition code flags.
Examples
SMULL R0, R4, R5 ; Multiplies R4 and R5, truncates top 32 bits
; and writes to R0
SMULLR R6, R2 ; Multiplies R6 and R2, rounds the top 32 bits
; and writes to R6.
12.6.6.9 SMUAD and SMUSD
Signed Dual Multiply Add and Signed Dual Multiply Subtract
Syntax
op
{X}{
cond
}
Rd
,
Rn
,
Rm
where:
op
is one of:
SMUAD Signed Dual Multiply Add.
SMUADX Signed Dual Multiply Add Reversed.
SMUSD Signed Dual Multiply Subtract.
SMUSDX Signed Dual Multiply Subtract Reversed.
If
X
is present, the multiplications are bottom × top and top × bottom.
If the
X
is omitted, the multiplications are bottom × bottom and top × top.
cond
is an optional condition code, see
“Conditional Execution”
.
Rd
is the destination register.
Rn, Rm
are registers holding the first and second operands.