AT89C5131A-M(2005) Ver la hoja de datos (PDF) - Atmel Corporation

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AT89C5131A-M
(Rev.:2005)

8-bit Flash Microcontroller with Full Speed USB Device

Atmel Corporation 

Dual Data Pointer

Register

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

size.

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

nal data memory location. There are two 16-bit DPTR registers that address the external

memory, and a single bit called DPS = AUXR1.0 (see Table 34) that allows the program

code to switch between them (see Figure 10).

Figure 10. Use of Dual Pointer

External Data Memory

7

0

DPS

AUXR1(A2H)

DPTR1

DPTR0

DPH(83H) DPL(82H)

Table 34. AUXR1 Register

AUXR1- Auxiliary Register 1(0A2h)

7

6

5

4

3

2

1

0

-

-

ENBOOT

-

GF3

0

-

DPS

Bit

Bit

Number Mnemonic Description

7

-

Reserved

The value read from this bit is indeterminate. Do not set this bit.

6

-

Reserved

The value read from this bit is indeterminate. Do not set this bit.

Enable Boot Flash

5

ENBOOT Cleared to disable boot ROM.

Set to map the boot ROM between F800h - 0FFFFh.

4

-

Reserved

The value read from this bit is indeterminate. Do not set this bit.

3

GF3 This bit is a general-purpose user flag.

2

0

Always cleared.

1

-

Reserved

The value read from this bit is indeterminate. Do not set this bit.

Data Pointer Selection

0

DPS Cleared to select DPTR0.

Set to select DPTR1.

Reset Value = XX[BLJB]X X0X0b

Not bit addressable

a. Bit 2 stuck at 0; this allows to use INC AUXR1 to toggle DPS without changing GF3.

26 AT89C5130A/31A-M

4337C–USB–02/05

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