6.93.2 Status Register (SREG) and Boolean Formula

H

Rd3 ∧ Rr3 ∨ Rr3 ∧ R3 ∨ R3 ∧ Rd3

Set if there was a borrow from bit 3; cleared otherwise.

S

N ⊕ V, for signed tests.

V

Rd7 ∧ Rr7 ∧ R7 ∨ Rd7 ∧ Rr7 ∧ 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 ∧ Z

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

C

Rd7 ∧ Rr7 ∨ Rr7 ∧ R7 ∨ R7 ∧ Rd7

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

R (Result) equals Rd after the operation.

Example:

                        ; Subtract r1:r0 from r3:r2
      sub   r2,r0       ; Subtract low byte
      sbc   r3,r1       ; Subtract with carry high byte

Words

1 (2 bytes)