Status Register (SREG) 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

Set if MSB of the result is set; cleared otherwise.

Z

R7 • R6 • R5 • R4 • R3 • R2 • R1 • R0 • Z

Previous value remains unchanged when the result is zero; cleared otherwise.

C

Rd7 • K7 + K7 • R7 + R7 • Rd7

Set if the absolute value of the constant plus previous carry is larger than the absolute value of Rd; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

 ; Subtract $4F23 from r17:r16
 subi r16,$23 ; Subtract low byte
 sbci r17,$4F ; Subtract with carry high byte