Datasheet

29
T89C51AC2
4127D–8051–02/03
Reset Value = X00X 1100b
Not bit addressable
Table 19. AUXR1 Register
AUXR1 (S:A2h)
Auxiliary Control Register 1
Reset Value = XXXX 00X0b
Note: 1. ENBOOT is initialized with the invert BLJB at reset. See In-System Programming
section.
1EXTRAM
Internal/External RAM (00h - FFh)
access using MOVX @ Ri/@ DPTR
0 - Internal XRAM access using MOVX @ Ri/@ DPTR.
1 - External data memory access.
0A0
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.
76543210
- - 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.
5ENBOOT
(1)
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.
3GF3General-purpose Flag 3
20
Always Zero
This bit is stuck to logic 0 to allow INC AUXR1 instruction without affecting GF3
flag.
1-Reserved for Data Pointer Extension.
0DPS
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