124. SUBI – Subtract Immediate
124.1. Description
Subtracts a register and a constant, and places the result in the destination register Rd. This instruction is
working on Register R16 to R31 and is very well suited for operations on the X, Y, and Z-pointers.
Operation:
(i) Rd ← Rd - K
Syntax: Operands: Program Counter:
(i) SUBI Rd,K 16 ≤ d ≤ 31, 0 ≤ K ≤ 255 PC ← PC + 1
16-bit Opcode:
0101 KKKK dddd KKKK
124.2. Status Register and Boolean Formula
I T H S V N Z C
– – ⇔ ⇔ ⇔ ⇔ ⇔ ⇔
H Rd3 • K3 + K3 • R3 + R3 • Rd3
Set if there was a borrow from bit 3; cleared otherwise.
S N ⊕ V, for signed tests.
V Rd7 • K7 • R7 + Rd7 • K7 • R7
Set if two’s complement overflow resulted from the operation; cleared otherwise.
N R7
Set if MSB of the result is set; cleared otherwise.
Z R7 • R6 • R5 • R4 • R3 • R2 • R1 • R0
Set if the result is $00; cleared otherwise.
C Rd7 • K7 + K7 • R7 + R7 • Rd7
Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.
R (Result) equals Rd after the operation.
Example:
subi r22,$11 ; Subtract $11 from r22
brne noteq ; Branch if r22<>$11
...
noteq: nop ; Branch destination (do nothing)
Atmel AVR Instruction Set Manual [OTHER]
Atmel-0856L-AVR-Instruction-Set-Manual_Other-11/2016
183
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