at89c5131 ATMEL Corporation, at89c5131 Datasheet - Page 24

• Manufacturer Part Number: at89c5131
• Description: 8-bit Flash Microcontroller With Full Speed Usb Device At89c5131
• Manufacturer: ATMEL Corporation

Dual Data Pointer
Register
Figure 10. Use of Dual Pointer
24
AT89C5131
7
AUXR1(A2H)
DPS
0
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 32) that allows the program
code to switch between them (see Figure 10).
Table 32. AUXR1 Register
AUXR1- Auxiliary Register 1(0A2h)
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.
Number
Bit
7
6
5
4
3
2
1
0
7
-
Mnemonic
DPH(83H) DPL(82H)
ENBOOT
GF3
DPS
Bit
0
-
-
-
-
6
-
DPTR1
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Enable Boot Flash
Cleared to disable boot ROM.
Set to map the boot ROM between F800h - 0FFFFh.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
This bit is a general-purpose user flag.
Always cleared.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Data Pointer Selection
Cleared to select DPTR0.
Set to select DPTR1.
ENBOOT
DPTR0
5
4
-
GF3
3
External Data Memory
2
0
1
-
4136C–USB–04/05
DPS
0