AT89LP6440 datasheet(27/194 Pages) ATMEL

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3706A–MICRO–9/09

AT89LP6440 - Preliminary

5.2.2

Data Pointer Operating Modes

The Dual Data Pointers on the AT89LP6440 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

–

DPS

Bit

543

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 is 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 and 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

MOVX

A, @DPTR0

MOVX

A, @DPTR1

MOVX

@DPTR0, A

MOVX

@DPTR1, A

MOVX

A, @DPTR1

MOVX

A, @DPTR0

MOVX

@DPTR1, A

MOVX

@DPTR0, A

MOVX

A, @DPTR0

MOVX

B, @DPTR1

MOVX

@DPTR0, A

MOVX

@DPTR1, B

MOVX

B, @DPTR1

MOVX

A, @DPTR0

MOVX

@DPTR1, B

MOVX

@DPTR0, A

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