W78LE54_06 Datasheet, PDF (7/26 Pages) Winbond – 8-BIT MICROCONTROLLER

W78LE54/W78L054A
4. Power-off Flag
***PCON - Power control (87H)
-
-
-
POF
GF1
GF0
PD
IDL
POF:
Power off flag. Bit is set by hardware when power on reset. It can be cleared by software
to determine chip reset is a warm boot or cold boot.
GF1, GF0: These two bits are general-purpose flag bits for the user.
PD:
Power down mode bit. Set it to enter power down mode.
IDL:
Idle mode bit. Set it to enter idle mode.
The power-off flag is located at PCON.4. This bit is set when VDD has been applied to the part. It can
be used to determine if a reset is a warm boot or a cold boot if it is subsequently reset by software.
Watchdog Timer
The Watchdog timer is a free-running timer which can be programmed by the user to serve as a
system monitor, a time-base generator or an event timer. It is basically a set of dividers that divide the
system clock. The divider output is selectable and determines the time-out interval. When the time-out
occurs a system reset can also be caused if it is enabled. The main use of the Watchdog timer is as a
system monitor. This is important in real-time control applications. In case of power glitches or electro-
magnetic interference, the processor may begin to execute errant code. If this is left unchecked the
entire system may crash. The watchdog time-out selection will result in different time-out values
depending on the clock speed. The Watchdog timer will de disabled on reset. In general, software
should restart the Watchdog timer to put it into a known state. The control bits that support the
Watchdog timer are discussed below.
Watchdog Timer Control Register
Bit:
7
6
5
4
ENW CLRW WIDL -
3
2
1
0
-
PS2 PS1 PS0
Mnemonic: WDTC
Address: 8FH
ENW : Enable watch-dog if set.
CLRW : Clear watch-dog timer and prescaler if set. This flag will be cleared automatically
WIDL : If this bit is set, watch-dog is enabled under IDLE mode. If cleared, watch-dog is disabled
under IDLE mode. Default is cleared.
PS2, PS1, PS0: Watch-dog prescaler timer select. Prescaler is selected when set PS2~0 as follows:
Publication Release Date: December 4, 2006
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Revision A6