
74
AT89C51ID2
4289C–8051–11/05
pins, the instruction immediately following the instruction that activated the Power-Down
mode should not write to a Port pin or to the external RAM.
Note:
Exit from power-down by reset redefines all the SFRs, but does not affect the internal
RAM content.
Table 57. Pin Conditions in Special Operating Modes
Mode
Port 0
Port 1
Port 2
Port 3
Port 4
ALE
PSEN#
Reset
Floating
High
Idle
(internal
code)
Data
High
Idle
(external
code)
Floating
Data
High
Power-
Down(inter
nal code)
Data
Low
Power-
Down
(external
code)
Floating
Data
Low