82. MULS – Multiply Signed
82.1. Description
This instruction performs 8-bit × 8-bit → 16-bit signed multiplication.
Rd Rr R1 R0
Multiplicand
×
Multiplier
→
Product High Product Low
8 8 16
The multiplicand Rd and the multiplier Rr are two registers containing signed numbers. The 16-bit signed
product is placed in R1 (high byte) and R0 (low byte).
This instruction is not available in all devices. Refer to the device specific instruction set summary.
Operation:
(i) R1:R0 ← Rd × Rr (signed ← signed × signed)
Syntax: Operands: Program Counter:
(i) MULS Rd,Rr 16 ≤ d ≤ 31, 16 ≤ r ≤ 31 PC ← PC + 1
16-bit Opcode:
0000 0010 dddd rrrr
82.2. Status Register (SREG) and Boolean Formula
I T H S V N Z C
– – – – – – ⇔ ⇔
C R15
Z R15 • R14 • R13 • R12 • R11 • R10 • R9 • R8R7 • R6 • R5 • R4 • R3 • R2 • R1 • R0
Set if the result is $0000; cleared otherwise.
R (Result) equals R1,R0 after the operation.
Example:
muls r21,r20 ; Multiply signed r21 and r20
mov w r20,r0 ; Copy result back in r21:r20
Words 1 (2 bytes)
Cycles 1
Atmel AVR Instruction Set Manual [OTHER]
Atmel-0856L-AVR-Instruction-Set-Manual_Other-11/2016
126
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