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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Reset and Initialisation
Reset and Initialisation
Watchdog Reset
All devices contain a Watchdog Timer which is used as a protection feature. The Watchdog
Timer has to be periodically cleared by the application program and prevented from overflowing
during normal MCU operation. However should the program enter an endless loop or should
external environmental conditions such as noise causes the device to jump to unpredicted program
locations, the Watchdog Timer will overflow from FFFFh to 0000h, and generate an MCU reset.
Refer to the Watchdog Timer section for more details regarding the Watchdog Timer operation.
When a Watchdog Reset occurs the WDTS bit in the IP0 register will be set to indicate the reset
source. Note that this bit must be reset by the application program.
IP0 Register
SFR Address: B8h
Bit
7
6
5
4
3
2
1
0
Name
—
WDTS
PT�
PS0
PT1
PX1
PT0
PX0
R/W
—
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
—
0
0
0
0
0
0
0
Bit 7
Unimplemented, read as “0”
Bit 6
WDTS:
Watchdog timer reset indication flag
0: No Watchdog timer reset
1: Watchdog timer reset
This bit must be cleared by the application program as it will not be automatically
cleared by hardware.
Bit 5
PT2:
Timer 2 Interrupt priority
Described elsewhere
Bit 4
PS0:
Serial Port 0 Interrupt priority
Described elsewhere
Bit 3
PT1:
Timer 1 Interrupt priority
Described elsewhere
Bit 2
PX1:
External interrupt 1 priority
Described elsewhere
Bit 1
PT0:
Timer 0 Interrupt priority
Described elsewhere
Bit 0
PX0:
External interrupt 0 priority
Described elsewhere