4182K–CAN–05/06
AT89C51CC03
Bit
Bit
Number Mnemonic Description
ERAM size:
Accessible size of the ERAM
XRS 2:0 ERAM size
000 256 Bytes
001 512 Bytes
4-2
XRS1-0 010
768 Bytes
011
1024 Bytes
100 1792 Bytes
101 2048 Bytes (default configuration after reset)
110
Reserved
111
Reserved
Internal/External RAM (00h - FFh)
1
EXTRAM
access using MOVX @ Ri/@ DPTR
0 - Internal ERAM access using MOVX @ Ri/@ DPTR.
1 - External data memory access.
Disable/Enable ALE)
0
A0
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.
Reset Value = X001 0100b
Not bit addressable
Table 8. AUXR1 Register
AUXR1 (S:A2h)
Auxiliary Control Register 1
7
6
5
4
3
2
1
0
-
-
ENBOOT
-
GF3
0
-
DPS
Bit
Number
7-6
5
4
Bit
Mnemonic Description
-
Reserved
The value read from these bits is indeterminate. Do not set these bits.
Enable Boot Flash
ENBOOT Set this bit for map the boot Flash between F800h -FFFFh
Clear this bit for disable boot Flash.
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
GF3 General-purpose Flag 3
Always Zero
2
0
This bit is stuck to logic 0 to allow INC AUXR1 instruction without affecting GF3
flag.
1
-
Reserved for Data Pointer Extension.
Data Pointer Select Bit
0
DPS Set to select second dual data pointer: DPTR1.
Clear to select first dual data pointer: DPTR0.
Reset Value = XXXX 00X0b
29