Motorola DSP96002 - Manual (Page 680)

MOTOROLA DSP96002 USER’S MANUAL B-161
;
; Round toward -infinity
;
_rminf jclr #31,d6.l,_lmove ; no rounding if positive
_addone move #$800,d7.l ; get increment number
add d7,d1 ; add one to lsb
jcc _acar ; jump if no carry
inc d3 ; increment mantr.high
_acar jcc _lmove ; jump if result normalized
lsr d3 ; shift right mantr.high
ror d1 ; shift right mantr.low
inc d6 ; increment expr
;
; Check if Result is Infinity
;
move #emsk,d7.l ; get exp mask
move d6.l,d5.l ; get expr
and d7,d5 ; delete tags
cmp d7,d5 ; check for max exp
jne _lmove ; jump if no overflow
move #0,d1.l ; set result to infinity
move #0,d1.m ; "
ori #$10,ccr ; set infinity bit
ori #$09,ier ; set OVF and INX bits in IER
ori #$09,er ; set OVF and INX bits in ER
jmp _emove ; get infinity exponent
;
; Get Result in D1
;
_lmove move d3.l,d1.m ; move mantr.high to d1
_emove move d6.l,d1.h ; move expr to d1
_done nop ;
nop ;
nop ;
rts ; end of subroutine
endsec
B.4.2 IEEE Double Precision Subtraction
;
; Double Precision IEEE floating-point Subtraction
;
; D0 - D1
→
D1
;
;
;
; Alters Data ALU Registers
; d0.h d0.m d0.l
; d1.h d1.m d1.l
; d2.m d2.l
; d3.l