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R16
Set if bit 15 of the result before left shift is set; cleared otherwise.
R15 • R14 • R13 • R12 • R11 • R10 • R9 • R8R7 • R6 • R5 • R4 • R3 • R2 • R1 • R0
Set if the result is $0000; 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 r19:r18, r1:r0
fmul r22, r20 ;(al * bl) << 1
adc r18, r2
movw r17:r16, r1: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