t89c51rd2-slscl ATMEL Corporation, t89c51rd2-slscl Datasheet - Page 13

• Manufacturer Part Number: t89c51rd2-slscl
• Description: 0 To 40 Mhz Flash Programmable 8-bit Microcontroller
• Manufacturer: ATMEL Corporation

Dual Data Pointer
Register Ddptr
Figure 3. Use of Dual Pointer
4243G–8051–05/03
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/bit0 (See Table 5.) that allows the program code to switch between them
(Refer to Figure 3).
Table 5. AUXR1: Auxiliary Register 1
1.
Address 0A2H
Symbol
AUXR1
DPS
GF3
-
User software should not write 1s to reserved bits. These bits may be used in future 8051
2. Bit 2 stuck at 0; this allows to use INC AUXR1 to toggle DPS without changing GF3.
DPH(83H) DPL(82H)
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.
Function
Not implemented, reserved for future use.
Data Pointer Selection.
This bit is a general purpose user flag
Reset value
DPTR1
DPS
0
1
DPTR0
Operating Mode
DPTR0 Selected
DPTR1 Selected
X
-
X
-
(2)
.
X
-
(1)
External Data Memory
X
-
GF3
0
T89C51RD2
0
0
X
-
DPS
0
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