at89c51rd2-smsum ATMEL Corporation, at89c51rd2-smsum Datasheet - Page 25

• Manufacturer Part Number: at89c51rd2-smsum
• Description: 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

4235J–8051–01/08
Reset Value = 0X00 1000
Not bit addressable
Number
Bit
1
0
Mnemonic
EXTRAM
Bit
AO
Description
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.
AT89C51RD2/ED2
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