Datasheet

4235K–8051–05/08

AT89C51RD2/ED2

Reset Value = 0X00 1000

Not bit addressable

1 EXTRAM

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.

0 AO

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.

Bit

Number

Bit

Mnemonic Description