RV-4162 Datasheet, PDF (20/39 Pages) MICORO CRYSTAL SWITZERLAND – Ultra Small Real Time Clock

Micro Crystal
Ultra Small Real Time Clock / Calendar Module
RV-4162
4.3. WATCHDOG TIMER
The Watchdog Timer can be used to detect an out-of-control microprocessor or deadlock of the Interface
communication. The function of the Interface Watchdog Timer is based on internal Timer / Counter which is
periodically reset by the internal control logic. If the control logic does not reset the Watchdog Timer within the
programmed time-out period, the RV-4162 detects an Interface time-out and sets Watchdog Flag (WDF = 1, bit 7,
in register Flags 0Fh) and generates an interrupt on INT pin 6.
The user programs the Watchdog Timer by setting the desired amount of time-out into the Watchdog register at
address 09h, a value of 00h will disable the watchdog function until it is again programmed to a new value.
The amount of time-out is then determined by selecting a Watchdog Timer Source Clock WD2 - WD0 and the
multiplication with the Watchdog Multiplier value WDM4 - WDM0.
 Bits WDM4 - WDM0 store a binary coded Watchdog Multiplier value.
 Bits WD2 - WD0 select the Watchdog Timer Clock Source.
For example: writing 00001110 in the Watchdog register = 3 x 1 second or 3 seconds.
Watchdog (address 09h…bits description)
Address
Function
Bit 7
09h
Watchdog
WD2
Bit 6
WDM4
Bit 5
WDM3
Bit 4
WDM2
Bit 3
WDM1
Bit 2
WDM0
Bit 1
WD1
Bit 0
WD0
Bit
7 to 0
Symbol
Watchdog
7, 1, 0
WD2 / WD1 / WD0
6 to 2
WDM4
0
0
WDM3
0
0
1
1
WD2
0
0
0
0
1
1
1
1
1
1
WD1
0
0
1
1
0
0
1
1
WDM4 to WDM0
WDM2
0
0
…
1
1
WDM1
0
0
1
1
WD0
0
1
0
1
0
1
0
1
WDM0
0
1
0
1
Value
000
001
010
011
100
101
110
111
Value
00h
000
-
100
0 to 31
Value
00h
01d
…
30d
31d
Description
A value of 00h disables Watchdog Timer function
Watchdog Timer Clock Source: 16Hz / 4Hz / 1 Hz / ¼ Hz / ¹/60 Hz
This register holds the binary coded Watchdog Multiplier value
Description
Setting “00000” with any combination of WD2 - WD0, other than “000”, will
result in an immediate watchdog time-out
Defines binary coded Watchdog Multiplier value
Timer Clock Source
Time
16 Hz
62.5ms
4 Hz
250 ms
1 Hz
1 second
¼ Hz
4 seconds
1_{/60 Hz}
1 minute
Invalid combination, will not enable Watchdog Timer
Invalid combination, will not enable Watchdog Timer
Invalid combination, will not enable Watchdog Timer
The Watchdog time-out period starts when the I²C interface communication is initiated. If the control logic does not
reset the Watchdog Timer within the programmed time-out period, the RV-4162 detects an Interface time-out and
sets the Watchdog Flag (WDF = 1, bit 7, in register Flags 0Fh) and generates an interrupt on INT pin 6.
The Watchdog Timer can only be reset by having the microprocessor perform a WRITE to the Watchdog Register
09h. The time-out period then starts over.
Should the Watchdog Timer time-out, any value may be written to the watchdog register in order to clear the INT
pin 6. A value of 00h will disable the watchdog function until it is again programmed to a new value. A READ of the
flags register will reset the Watchdog Flag (bit 7; register 0Fh). The watchdog function is automatically disabled
upon power-up, and the Watchdog Register is cleared.
Note: A WRITE to any clock register will restart the Watchdog Timer.
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