Motorola DSP96002 - Manual (Page 705)

B-186 DSP96002 USER’S MANUAL MOTOROLA
inc d4.l ;increment the exponent
jmp leave ;check for overflow
;
; Calculate the result assuming that c(r0) > 0 and X < 0
;
apos cmp d2,d0 ;compare mantissas
jne decide ;if ms’s are equal, test ls’s
cmp d3,d1 #1,d7.l ;compare ls of mantissas
jeq dp_clr ;clear reg_a if same magnitude
decide jcc r1fromr0 ;if c(r0) > c(r1), c(r0) - c(r1)
jmp r0fromr1 ;subtract c(r0) from c(r1)
r1fromr0 sub d3,d1 ;subtract c(r1) from c(r0)
subc d2,d0 ;calculate c(r0)_ms
jmp subnorm ;normalize result
;
; Shift the c(r0) 64 bit significand
;
dshifta move d5.l,d0.h ;# of shifts in .h register
lsr d0.h,d1 d0.l,d6.l ;shift ls, copy ms
lsr d0.h,d0 #32,d7.l ;shift ms
sub d5,d7 ;calc. # opposite dir. shifts
move d7.l,d0.h ;# of shifts in .h register
lsl d0.h,d6 ;get bits to be shifted to ls
or d6,d1 ;shift in bits from ms to ls
jmp addmant
;
; Shift the c(r1) 64 bit significand
;
dshiftx move d6.l,d0.h ;# of shifts in .h register
lsr d0.h,d3 d2.l,d1.h ;shift ls, copy ms
lsr d0.h,d2 #32,d7.l ;shift ms
sub d6,d7 d1.h,d6.l ;calc. # opposite dir. shifts
move d7.l,d0.h ;# of opposite dir. shifts
lsl d0.h,d6 ;get bits to be shifted to ls
or d6,d3 ;shift in bits from ms to ls
jmp addmant
;
; Replace c(r0) with c(r1) (c(r0) is insignificant compared to c(r1))
;
aequalx move x:(r1+sign),d0.l
move d0.l,x:(r0+sign) ;c(r0)_sign
←
c(r1)_sign
move d3.l,x:(r0+ls) ;c(r0)_ls
←
c(r1)_ls
move d2.l,x:(r0+ms) ;c(r0)_ms
←
c(r1)_ms
move d4.l,x:(r0) ;c(r0)_exp
←
c(r1)_exp
;
; Leave c(r0) unchanged (c(r1) is insignificant compared to c(r0))
;
aequala rts
;
; Place the result of the operation in c(r0)
;
leave move d0.l,x:(r0+ms) ;store c(r0)_ms
move d1.l,x:(r0+ls) ;store c(r0)_ls
move d4.l,x:(r0) ;store c(r0) exponent