mc68hc05l25 Freescale Semiconductor, Inc, mc68hc05l25 Datasheet - Page 84

• Manufacturer Part Number: mc68hc05l25
• Description: M68hc05 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Time Base
Time base interrupt flag (TBIF) is set every period and an interrupt is requested if the enable bit (TBIE) is
set. The clock divided by 128, 4096, 8192, or 16,384 is used to set TBIF, and this clock is selected by the
TBR1 and TBR0 bits in the TBCR2 register.
9.2.4 COP
The computer operating properly (COP) watchdog timer on the MC68HC05L25 is controlled by the COPE
and COPC bits in the TBCR2 register.
The COP uses the same clock as TBI that is selected by the TBR1 and TBR0 bits. The TBI clock is divided
by four and overflow of this divider generates COP timeout reset if the COP enable (COPE) bit is set. The
COP timeout reset has the same vector address as power-on and external RESET. To prevent the COP
timeout, the COP divider is cleared by writing a one to the COP clear (COPC) bit.
When the time base divider is driven by the OSC clock, the clock for the divider is suspended during stop
mode or when FOSCE is equal to zero. This may cause stretching of the COP period or no COP timeout
reset occurring when there is a processing error. It is recommended that the XOSC clock be used as the
clock source for time base to avoid these problems.
When the COP is enabled during stop mode and the time base is driven by the XOSC clock, the divider
does not stop counting and the COPC bit must be triggered to prevent the COP timeout. It is
recommended that the COP watchdog should be disabled for a system that must have intentional use of
the stop mode period longer than the COP timeout period.
84
TBR1 TBR0
TBR1
0
0
1
1
TBCR2
0
0
1
1
TBCR2
TBR0
0
1
0
1
0
1
0
1
TBCLK ÷ 4096
TBCLK ÷ 8192
TBCLK ÷ 128
TBCLK ÷
Divide
16,384
1573
Ratio
OSC = 4.0 MHz
Table 9-2. Time Base Interrupt Frequency
12.3
Min
393
786
Table 9-3. COP Timeout Period
MC68HC05L25 Data Sheet, Rev. 3.1
1048
2097
Max
16.4
524
OSC = 4.0 MHz
7.63
3.81
1.91
244
OSC = 4.1943 MHz
1500
11.7
Min
375
750
COP Period (ms)
OSC = 4.1943 MHz
Frequency (Hz)
1000
2000
Max
15.6
500
8.00
4.00
2.00
256
XOSC = 32.768 kHz
1500
11.7
Min
375
750
XOSC = 32.768 kHz
8.00
4.00
2.00
256
Freescale Semiconductor
1000
2000
Max
15.6
500