6.57.2 Status Register (SREG) and Boolean Formula

C

R16

Set if bit 15 of the result before the left shift is set; cleared otherwise.

Z

R15 ∧ R14 ∧ R13 ∧ R12 ∧ R11 ∧ R10 ∧ R9 ∧ R8∧R7 ∧ R6 ∧ R5 ∧ R4 ∧ R3 ∧ R2 ∧ R1 ∧ R0

Set if the result is 0x0000; cleared otherwise.

R (Result) equals R1,R0 after the operation.

Example:

;******************************************************************************
;* DESCRIPTION
;* Signed fractional multiply of two 16-bit numbers with 32-bit result.
;* USAGE
;* r19:r18:r17:r16 = ( r23:r22 * r21:r20 ) << 1
;******************************************************************************
fmuls16x16_32:
      clr      r2
      fmuls    r23, r21      ; ((signed)ah * (signed)bh) << 1
      movw     r18, r0
      fmul     r22, r20      ; (al * bl) << 1
      adc      r18, r2
      movw     r16, r0
      fmulsu   r23, r20      ; ((signed)ah * bl) << 1
      sbc      r19, r2
      add      r17, r0
      adc      r18, r1
      adc      r19, r2
      fmulsu   r21, r22      ; ((signed)bh * al) << 1
      sbc      r19, r2
      add      r17, r0
      adc      r18, r1
      adc      r19, r2
      ret

Words

1 (2 bytes)