EM6605 EM Microelectronic, EM6605 Datasheet - Page 9

• Manufacturer Part Number: EM6605
• Description: 4 bit Microcontroller
• Manufacturer: EM Microelectronic

Table 8.Prescaler control register - PRESC
5. Watchdog timer
If for any reason the CPU crashes, then the watchdog timer can detect this situation and output a system
reset signal. This function can be used to detect program overrun. For normal operation the watchdog
timer must be reset periodically by software at least once every three seconds (*f1) (CLK = 32kHz) or a
system reset signal is generated to CPU and periphery. The watchdog is active during STANDBY. The
watchdog reset function can be deactivated by setting the NoWD bit to 1 in the Option register.
In worst case because of prescaler reset function WD time-out can come down to 2 seconds.
The watchdog timer is reset by writing 1 to the WDRST bit. Writing 0 to WDRST has no effect.
The watchdog timer also operates in STANDBY mode. It is therefore necessary to reset it if this mode
continues for more than three seconds (*f1). One method of doing this is to reset it with the prescaler ck[1]
interrupt (1Hz *f1 such, that the watchdog is reset every second).
Table 9.Watchdog register - WD
Bit
3
2
1
0
Bit
3
2
1
0
Name
MTim
PRST
PSF1
PSF0
Name
WDRST
Slmask
WD1
WD0
Reset
0
-
0
0
Reset
-
-
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
R
Timer/Counter Interrupt Mask
Prescaler reset
Prescaler Interrupt select 1
Prescaler Interrupt select 0
Watchdog timer reset
SLEEP mask bit
WD Timer data ck[1]/4 (1/4Hz *f1)
WD Timer data ck[1]/2 (1/2 Hz *f1)
Description
Description
© EM Microelectonic-Marin SA, 02/99, Rev. B/243
EM6605
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