AT89LP428-20MU ATMEL [ATMEL Corporation], AT89LP428-20MU Datasheet - Page 18

• Manufacturer Part Number: AT89LP428-20MU
• Description: 8-bit Microcontroller with 4K/8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

5.1.1
18
AT89LP428/828
Data Pointer Update
For assemblers that do not support this notation, the 0A5H prefix must be declared in-line:
A summary of data pointer instructions with fast context switching is listed in
Table 5-1.
The Dual Data Pointers on the AT89LP428/828 include two additional features that control how
the data pointers are updated. The data pointer decrement bits, DPD1 and DPD0 in DPCF, con-
figure the INC DPTR instruction to act as DEC DPTR. The resulting operation will depend on
DPS as shown in
Table 5-2.
The data pointer update bits, DPU1 and DPU0, allow MOVX @DPTR and MOVC @DPTR
instructions to update the selected data pointer automatically in a post-increment or post-
decrement fashion. The direction of update depends on the DPD1 and DPD0 bits as shown in
Table
JMP @A+DPTR
MOV DPTR, #data16
MOV/DPTR, #data16
INC DPTR
INC/DPTR
MOVC A,@A+DPTR
MOVC A,@A+/DPTR
MOVX A,@DPTR
MOVX A,@/DPTR
MOVX @DPTR, A
MOVX @/DPTR, A
DPD1
EX:
0
0
1
1
5-3.
Instruction
DB
INC
DPD0
Data Pointer Instructions
INC DPTR Behavior
0
1
0
1
Table
0A5H
DPTR
5-2.
DEC DPTR0
DEC DPTR0
INC DPTR0
INC DPTR0
INC DPTR
JMP @A+DPTR0
MOV DPTR0, #data16
MOV DPTR1, #data16
INC DPTR0
INC DPTR1
MOVC A,@A+DPTR0
MOVC A,@A+DPTR1
MOVX A,@DPTR0
MOVX A,@DPTR1
MOVX @DPTR0, A
MOVX @DPTR1, A
DPS = 0
; equivalent to INC /DPTR
DEC DPTR1
DEC DPTR1
INC DPTR1
INC DPTR1
INC /DPTR
DPS = 0
Operation
Operation
DEC DPTR1
DEC DPTR1
INC DPTR1
INC DPTR1
INC DPTR
JMP @A+DPTR1
MOV DPTR1, #data16
MOV DPTR0, #data16
INC DPTR1
INC DPTR0
MOVC A,@A+DPTR1
MOVC A,@A+DPTR0
MOVX A,@DPTR1
MOVX A,@DPTR0
MOVX @DPTR1, A
MOVX @DPTR0, A
DPS = 1
DPS = 1
Table
DEC DPTR0
DEC DPTR0
3654A–MICRO–8/09
INC DPTR0
INC DPTR0
INC /DPTR
5-1.