102. SBIW – Subtract Immediate from Word
102.1. Description
Subtracts an immediate value (0-63) from a register pair and places the result in the register pair. This
instruction operates on the upper four register pairs, and is well suited for operations on the Pointer
Registers.
This instruction is not available in all devices. Refer to the device specific instruction set summary.
Operation:
(i) Rd+1:Rd ← Rd+1:Rd - K
Syntax: Operands: Program Counter:
(i) SBIW Rd+1:Rd,K d ∈ {24,26,28,30}, 0 ≤ K ≤ 63 PC ← PC + 1
16-bit Opcode:
1001 0111 KKdd KKKK
102.2. Status Register (SREG) and Boolean Formula
I T H S V N Z C
– – – ⇔ ⇔ ⇔ ⇔ ⇔
S N ⊕ V, for signed tests.
V R15 • Rdh7
Set if two’s complement overflow resulted from the operation; cleared otherwise.
N R15
Set if MSB of the result is set; cleared otherwise.
Z R15 • R14 • R13 • R12 • R11 • R10 • R9 • R8R7 • R6 • R5 • R4 • R3 • R2 • R1 • R0
Set if the result is $0000; cleared otherwise.
C R15 • Rdh7
Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.
R (Result) equals Rdh:Rdl after the operation (Rdh7-Rdh0 = R15-R8, Rdl7-Rdl0=R7-R0).
Example:
sbiw r25:r24,1 ; Subtract 1 from r25:r24
sbiw YH:YL,63 ; Subtract 63 from the Y-pointer(r29:r28)
Words 1 (2 bytes)
Atmel AVR Instruction Set Manual [OTHER]
Atmel-0856L-AVR-Instruction-Set-Manual_Other-11/2016
154
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