W77C32 Datasheet, PDF (44/78 Pages) Winbond – 8 BIT MICROCONTROLLER

W77C32/W77C032A
The W77C032 can be woken from the Power Down mode by forcing an external interrupt pin activated,
provided the corresponding interrupt is enabled, while the global enable(EA) bit is set and the external
input has been set to a level detect mode. If these conditions are met, then the low level on the external
pin re-starts the oscillator. Then device executes the interrupt service routine for the corresponding
external interrupt. After the interrupt service routine is completed, the program execution returns to the
instruction after the one which put the device into Power Down mode and continues from there. When
RGSL(EXIF.1) bit is set to 1, the CPU will use the internal RC oscillator instead of crystal to exit Power
Down mode. The microcontroller will automatically switch from RC oscillator to crystal after clock is
stable. The RC oscillator runs at approximately 2−4 MHz. Using RC oscillator to exit from Power Down
mode saves the time for waiting crystal start-up. It is useful in the low power system which usually be
awakened from a short operation then returns to Power Down mode.
Table 5. Status of external pins during Idle and Power Down
MODE
PROGRAM
MEMORY
ALE
PSEN ^PORT0
Idle
Internal
1
1
Data
Idle
External
1
1
Float
Power Down
Internal
0
0
Data
Power Down
External
0
0
Float
PORT1
Data
Data
Data
Data
PORT2 PORT3
Data
Address
Data
Data
Data
Data
Data
Data
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