Motorola DSP96002 - Manual (Page 593)

B-74 DSP96002 USER’S MANUAL MOTOROLA
B.1.40.2 64 Bit Block Transfer
A more efficient implementation of BITBLT may be performed by transferring 64 bits at a time. Thus, the
value of COUNT specifies the number of 64 bit transfers (two 32 bit words).
64 Bit Block Transfer Program ICycles
BITBLT Words
org x:0
source ds 1 ;source address
dest ds 1 ;destination address
offset ds 1 ;bit number start (0-31)
count ds 1 ;number of 64 bit source words
org p:$50
move x:offset,d0.l ;get output bit position 2 2
move x:offset,d0.l ;get output bit position 2 2
move #32,d1.l ;get 32 2 2
sub d0,d1 x:source,r0 ;32-offset, get source address 2 2
move x:dest,r1 ;point to destination address 2 2
move d1.l,d1.h ;move shift factor 1 1
lsl d1,d4 d0.l,d0.h ;shift bits, move shift factor 1 1
move x:count,n0 ;get source word count 2 2
move (r1)- ;backup pointer 1 1
move y:(r1)+,d6.l ;init pipe 1 1
move y:(r1)-,d4.l ;get first bits of dest 1 1
move y:(r0)+,d5.l ;get source bits 1 1
do n0,bitblt ;do transfer 2 3
lsr d1,d4 d6.l,y:(r1)+ 1 1
lsl d0,d5 d5.l,d3.l 1 1
or d4,d5 y:(r0)+,d6.l 1 1
lsr d1,d3 d5.l,y:(r1)+ 1 1
lsl d0,d6 d6.l,d4.l 1 1
or d3,d6 y:(r0)+,d5.l 1 1
bitblt
move d6.l,y:(r1)+ 1 1
lsr d1,d4 y:(r1),d5.l ;shift old bits, get dest bits 1 1
lsr d0,d5 ;shift dest bits 1 1
lsl d0,d5 ;shift dest bits back 1 1
or d4,d5 ;part of dest with source bits 1 1
move d5.l,y:(r1) ;save new destination bits 1 1
--- ---
Totals: 32 6N+27
Where N represents 64 bits transferred. At a 13.5 MIPS, a total of (13.5/6)*64 = 144 MBits/Second transfer
rate is possible.