Specifications

28
3706C–MICRO–2/11
AT89LP3240/6440
5.2.2 Data Pointer Operating Modes
The Dual Data Pointers on the AT89LP3240/6440 include three additional operating modes that
affect data pointer based instructions. These modes are controlled by bits in DSPR.
5.2.2.1 DPTR Redirect
The Data Pointer Redirect to B bit, DPRB (DSPR.0), allows MOVX and MOVC instructions to
use the B register as the data source/destination when the instruction references DPTR1 as
shown in
Table 5-6 and Table 5-7. DPRB can improve the efficiency of routines that must fetch
multiple operands from different RAM locations.
Table 5-5.
DPCF – Data Pointer Configuration Register
DPCF = A2H Reset Value = 0000 00X0B
Not Bit Addressable
DPU1 DPU0 DPD1 DPD0 SIGEN 0 – DPS
Bit76543210
Symbol Function
DPU1 Data Pointer 1 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR1 will also update
DPTR1 based on DPD1. If DPD1 = 0 the operation is post-increment and if DPD1 = 1 the operation is post-decrement.
When DPU1 = 0, DPTR1 is not updated.
DPU0 Data Pointer 0 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR0 will also update
DPTR0 based on DPD0. If DPD0 = 0 the operation is post-increment and if DPD0 = 1 the operation is post-decrement.
When DPU0 = 0, DPTR0 i
s not updated.
DPD1 Data Pointer 1 Decrement. When set, INC DPTR instructions targeted to DPTR1 will decrement DPTR1. When cleared,
INC DPTR instructions will increment DPTR1. DPD1 also determines the direction of auto-update for DPTR1 when
DPU1 = 1.
DPD0 Data Pointer 0 Decrement. When set, INC DPTR instructions targeted to DPTR0 will decrement DPTR0. When cleared,
INC DPTR instructions will increment DPTR0. DPD0 also determines the direction of auto-update for DPTR0 when
DPU0 = 1.
SIGEN Signature Enable. When SIGEN = 1 all MOVC @DPTR instructions a
nd all IAP accesses will target the signature array
memory. When SIGEN = 0, all MOVC and IAP accesses target CODE memory.
DPS Data Pointer Select. DPS selects the active data pointer for instructions that reference DPTR. When DPS = 0, DPTR will
target DPTR0 and /DPTR will target DPTR1. When DPS = 1, DPTR will target DPTR1 and /DPTR will target DPTR0.
Table 5-6. MOVX @DPTR Operating Modes
DPRB DPS
Equivalent Operation for MOVX
MOVX A, @DPTR MOVX @DPTR, A
DPTR /DPTR DPTR /DPTR
00
MOVX
A, @DPTR0
MOVX
A, @DPTR1
MOVX
@DPTR0, A
MOVX
@DPTR1, A
01
MOVX
A, @DPTR1
MOVX
A, @DPTR0
MOVX
@DPTR1, A
MOVX
@DPTR0, A
10
MOVX
A, @DPTR0
MOVX
B, @DPTR1
MOVX
@DPTR0, A
MOVX
@DPTR1, B
11
MOVX
B, @DPTR1
MOVX
A, @DPTR0
MOVX
@DPTR1, B
MOVX
@DPTR0, A