at89c51rc2-slsil ATMEL Corporation, at89c51rc2-slsil Datasheet - Page 25

• Manufacturer Part Number: at89c51rc2-slsil
• Description: 8-bit Microcontroller With 16k/ 32k Bytes Flash
• Manufacturer: ATMEL Corporation

Registers
4180E–8051–10/06
Table 19. AUXR Register
AUXR - Auxiliary Register (8Eh)
Reset Value = XX0X 00’HSB. XRAM’0b (see Table 65)
Not bit addressable
Number
DPU
Bit
7
7
6
5
4
3
2
1
0
Mnemonic Description
EXTRAM
XRS1
XRS0
DPU
Bit
M0
AO
6
-
-
-
Disable Weak Pull-up
Cleared to activate the permanent weak pull up when latch data is logical 1
Set to disactive the weak pull-up (reduce power consumption)
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.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
XRAM Size
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.
XRS1 XRS0 XRAM size
0
0
1
1
M0
5
0
1
0
1
256 Bytes (default)
512 Bytes
768 Bytes
1024 Bytes
4
-
XRS1
3
AT89C51RB2/RC2
XRS0
2
EXTRAM
1
AO
0
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