AT89C51RB2-RLTCM ATMEL [ATMEL Corporation], AT89C51RB2-RLTCM Datasheet - Page 81

• Manufacturer Part Number: AT89C51RB2-RLTCM
• Description: 8-bit Microcontroller with 16K/ 32K Bytes Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Figure 33. Power-down Exit Waveform
Table 62. State of Ports
4180B–8051–04/03
Power Down
Power Down
Mode
Idle
Idle
or
XTALB
XTALA
INT0
INT1
Program Memory
Active Phase
External
External
Internal
Internal
be the one following the instruction that puts the AT89C51RB2/RC2 into Power-down
mode.
Exit from Power-down by reset redefines all the SFRs, exit from Power-down by exter-
nal interrupt does no affect the SFRs.
Exit from Power-down by either reset or external interrupt does not affect the internal
RAM content.
Note:
Table 62 shows the state of ports during idle and power-down modes.
Port 0 can force a 0 level. A "one" will leave port floating.
ALE
If idle mode is activated with Power-down mode (IDL and PD bits set), the exit sequence
is unchanged, when execution is vectored to interrupt, PD and IDL bits are cleared and
idle mode is not entered.
1
1
0
0
Power-down Phase
PSEN
0
1
1
0
Port Data
Port Data
Oscillator Restart Phase
PORT0
Floating
Floating
(1)
(1)
Port Data
Port Data
Port Data
Port Data
PORT1
AT89C51RB2/RC2
Active Phase
Port Data
Port Data
Port Data
PORT2
Address
Port Data
Port Data
Port Data
Port Data
PORT3
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