EM6607 EM Microelectronic, EM6607 Datasheet - Page 12

• Manufacturer Part Number: EM6607
• Description: Ultra-low power microcontroller
• Manufacturer: EM Microelectronic

5
A built-in crystal oscillator circuit generates the system-operating clock for the CPU and peripheral circuits from an externally
connected crystal (typ. 32.768kHz) and trimmer capacitor (from Qin tw. V
oscillator circuit. In SLEEP mode the oscillator is stopped.
With Fout bit in PA3cnt register we can put the system 32.768 Hz frequency on STB/RST pin as output.
5.1
The input to the prescaler is the system clock signal. The
prescaler consists of a fifteen (15) element divider chain
which delivers clock signals for the peripheral circuits such
as the timer/counter, buzzer, I/O debouncers and edge
detectors, as well as generating prescaler interrupts.
The frequency of prescaler interrupts is software selectable, as shown in Table 8.
Table 9.
6
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 (CLK = 32kHz) or a system reset signal is generated to CPU and periphery. The
watchdog is active during STANDBY. Setting the NoWD bit to 1 in the Option register deactivates the watchdog-reset function.
In worst case because of prescaler reset function WD time-out can come down to 2 seconds.
Writing 1 to the WDRST bit resets the watchdog timer. 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. One method to do so is to use the prescaler 1Hz interrupt such, that the watchdog is reset every second.
Table 10.
Copyright © 2005, EM Microelectronic-Marin SA
Bit
3
2
1
0
Bit
3
2
1
0
Oscillator
Watchdog timer
Prescaler
Prescaler control register - PRESC
Watchdog register - WD
R
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
Description
Timer/Counter Interrupt Mask
Prescaler reset
Prescaler Interrupt select 1
Prescaler Interrupt select 0
Description
Watchdog timer reset
SLEEP mask bit
WD Timer data 1/4 Hz
WD Timer data 1/2 Hz
12
Table 8.
Interrupt frequency
mask(no interrupt)
1 Hz
8 Hz
32 Hz
Prescaler interrupts source
SS
). The regulated voltage, V
PSF1
0
0
1
1
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EM6607
PSF0
0
1
0
1
REG
, supplies the