Datasheet

26
AT89C51AC3
4383D–8051–02/08
Reset Value = X001 0100b
Not bit addressable
Table 8. AUXR1 Register
AUXR1 (S:A2h)
Auxiliary Control Register 1
Reset Value = XXXX 00X0b
4-2 XRS1-0
ERAM size:
Accessible size of the ERAM
XRS 2:0 ERAM size
000 256 Bytes
001 512 Bytes
010 768 Bytes
011 1024 Bytes
100 1792 Bytes
101 2048 Bytes (default configuration after reset)
110 Reserved
111 Reserved
1 EXTRAM
Internal/External RAM (00h - FFh)
access using MOVX @ Ri/@ DPTR
0 - Internal ERAM access using MOVX @ Ri/@ DPTR.
1 - External data memory access.
0 A0
Disable/Enable ALE)
0 - ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2
mode is used)
1 - ALE is active only during a MOVX or MOVC instruction.
7 6 5 4 3 2 1 0
- - ENBOOT - GF3 0 - DPS
Bit
Number
Bit
Mnemonic Description
7-6 -
Reserved
The value read from these bits is indeterminate. Do not set these bits.
5 ENBOOT
Enable Boot Flash
Set this bit for map the boot Flash between F800h -FFFFh
Clear this bit for disable boot Flash.
4 -
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3 GF3 General-purpose Flag 3
2 0
Always Zero
This bit is stuck to logic 0 to allow INC AUXR1 instruction without affecting GF3
flag.
1 - Reserved for Data Pointer Extension.
0 DPS
Data Pointer Select Bit
Set to select second dual data pointer: DPTR1.
Clear to select first dual data pointer: DPTR0.
Bit
Number
Bit
Mnemonic Description