Dallas DS87C550, User Manual Supplement

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DS87C550 High-Speed Microcontroller User’s Guide Supplement
68 of 93
INC DPTR
MOV DPTR, #data16
MOVC A, @A+DPTR
MOVX A, @DPTR
MOVX @DPTR, A
This feature allows further reduction of code for data movement operations, and therefore even higher
performance. The following example demonstrates the improved efficiency.
64 BYTE BLOCK MOVE WITH AUTO SELECT
; SH and SL are high and low bytes of the source address
; DH and DL are high and low bytes of the destination address
; DPS is the data pointer select bit. Reset condition is DPS = 0 (DPTR selected).
;
# of cycles
MOV R5, #64
; Number of bytes to move 3
MOV DPTR, #SHSL ; Load destination address & toggle select bit 2
MOV DPTR, #DHDL
; Load destination address & toggle select bit 2
;
; This loop is executed the number of times contained in R5 (i.e., 64)
MOVE:
MOVX A, DPTR
; Read source data byte & toggle select bit 2
MOVX @DPTR, A
; Store at destination & toggle select bit 2
INC DPTR
; Increment source address & toggle select bit 3
INC DPTR
; Increment destination address & toggle select bit 3
DJNZ R5, MOVE
; Finished with table 3
Total = 7 + (13*64) = 839
64 BYTE BLOCK MOVE WITHOUT AUTO SELECT
; SH and SL are high and low bytes of the source address
; DH and DL are high and low bytes of the destination address
; DPS is the data pointer select bit. Reset condition is DPS = 0 (DPTR selected).
;
# of cycles
MOV R5, #64
; Number of bytes to move 3
MOV DPTR, #SHSL
; Load source address 2
INC DPS
; Change active DPTR 2
MOV DPTR, #DHDL
; Load destination address 2
INC DPS
; Change active DPTR 2
;
; This loop is executed the number of times contained in R5 (i.e., 64)
MOVE:
MOVX A, DPTR
; Read source data byte 2
INC DPS
; Change active DPTR 2
MOVX @DPTR, A
; Store at destination 2
INC DPTR
; Increment destination address 3
INC DPS
; Change active DPTR 2
INC DPTR
; Increment destination address 3
INC DPS
; Change active DPTR 2