at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 24

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Registers
24
AT89C51RE2
Table 17. AUXR Register
AUXR - Auxiliary Register (8Eh)
Reset Value = XX01 1100b
Not bit addressable
Number
Bit
4-2
7
-
7
6
5
1
0
Mnemonic Description
EXTRAM
XRS2:0
Bit
M0
AO
6
-
-
-
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.
Pulse length
Cleared to stretch MOVX control: the RD/ and the WR/ pulse length is 6 clock
periods (default).
Set to stretch MOVX control: the RD/ and the WR/ pulse length is 30 clock
periods.
XRAM Size
XRS2 XRS1XRS0XRAM size
0
0
0
0
1
1
1
1
EXTRAM bit
Cleared to access internal XRAM using movx @ Ri/ @ DPTR.
Set to access external memory.
Programmed by hardware after Power-up regarding Hardware Security Byte
(HSB), default setting, XRAM selected.
ALE Output bit
Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if
X2 mode is used). (default) Set, ALE is active only during a MOVX or MOVC
instruction is used.
0
0
1
1
0
0
1
1
M0
5
0
1
0
1
0
1
0
1
256 bytes
512 bytes
768 bytes
1024 bytes
1792 bytes
2048 bytes
4096 bytes
8192 bytes (default)
XRS2
4
XRS1
3
XRS0
2
EXTRAM
1
7663B–8051–03/07
AO
0