AT80C51RA2-RLSIV datasheet(15/86 Pages) ATMEL

15 / 86 page

4188F–8051–01/08

AT/TS8xC51Rx2

5.4

Dual Data Pointer Register

The additional data pointer can be used to speed up code execution and reduce code size in a

number of ways.

The dual DPTR structure is a way by which the chip will specify the address of an external data

memory location. There are two 16-bit DPTR registers that address the external memory, and a

single bit called DPS = AUXR1/bit0 (Table 5-3) that allows the program code to switch between

them (Refer to Figure 5-3).

Figure 5-3.

Use of Dual Pointer

Table 5-3.

AUXR1: Auxiliary Register 1

External Data Memory

AUXR1(A2H)

DPS

DPH(83H) DPL(82H)

DPTR0

DPTR1

AUXR1

Address 0A2H

GF3

DPS

Reset value

Symbol

Function

Not implemented, reserved for future use (1)

User software should not write 1s to reserved bits. These bits may be used in future 8051 family

products to invoke new feature. In that case, the reset value of the new bit will be 0, and its

active value will be 1. The value read from a reserved bit is indeterminate.

GF3 will not be available on first version of the RC devices.

DPS

Data Pointer Selection.

DPS

Operating Mode

DPTR0 Selected

DPTR1 Selected

GF3

This bit is a general purpose user flag(2).

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