Specifications

27
3706C–MICRO–2/11
AT89LP3240/6440
A summary of data pointer instructions with fast context switching is listed inTable 5-2.
5.2.1 Data Pointer Update
The Dual Data Pointers on the AT89LP3240/6440 include two features that control how the data
pointers are updated. The data pointer decrement bits, DPD1 and DPD0 in DPCF, configure the
INC DPTR instruction to act as DEC DPTR. The resulting operation will depend on DPS as
shown in Table 5-3.
The data pointer u
pdate bits, DPU1 and DPU0, allow MOVX @DPTR and MOVC @DPTR
instructions to update the selected data pointer automatically in a post-increment or post-decre-
ment fashion. The direction of update depends on the DPD1 and DPD0 bits as shown in Table
5-4.
Table 5-2. Data Pointer Instructions
Instruction
Operation
DPS = 0 DPS = 1
JMP @A+DPTR JMP @A+DPTR0 JMP @A+DPTR1
MOV DPTR, #data16 MOV DPTR0, #data16 MOV DPTR1, #data16
MOV /DPTR, #data16 MOV DPTR1, #data16 MOV DPTR0, #data16
INC DPTR INC DPTR0 INC DPTR1
INC /DPTR INC DPTR1 INC DPTR0
MOVC A,@A+DPTR MOVC A,@A+DPTR0 MOVC A,@A+DPTR1
MOVC A,@A+/DPTR MOVC A,@A+DPTR1 MOVC A,@A+DPTR0
MOVX A,@DPTR MOVX A,@DPTR0 MOVX A,@DPTR1
MOVX A,@/DPTR MOVX A,@DPTR1 MOVX A,@DPTR0
MOVX @DPTR, A MOVX @DPTR0, A MOVX @DPTR1, A
MOVX @/DPTR, A MOVX @DPTR1, A MOVX @DPTR0, A
Table 5-3. Data Pointer Decrement Behavior
DPD1 DPD0
Equivalent Operation for INC DPTR and INC /DPTR
DPS = 0 DPS = 1
INC DPTR INC /DPTR INC DPTR INC /DPTR
0 0 INC DPTR0 INC DPTR1 INC DPTR1 INC DPTR0
0 1 DEC DPTR0 INC DPTR1 INC DPTR1 DEC DPTR0
1 0 INC DPTR0 DEC DPTR1 DEC DPTR1 INC DPTR0
1 1 DEC DPTR0 DEC DPTR1 DEC DPTR1 DEC DPTR0
Table 5-4. Data Pointer Auto-Update
DPD1 DPD0
Update Operation for MOVX and MOVC (DPU1 = 1 & DPU0 = 1)
DPS = 0 DPS = 1
DPTR /DPTR DPTR /DPTR
0 0 DPTR0++ DPTR1++ DPTR1++ DPTR0++
0 1 DPTR0-- DPTR1++ DPTR1++ DPTR0--
1 0 DPTR0++ DPTR1-- DPTR1-- DPTR0++
1 1 DPTR0-- DPTR1-- DPTR1-- DPTR0--