M68HC16 Z SERIES
SYSTEM INTEGRATION MODULE
USER’S MANUAL
5-27
is a block diagram of the watchdog timer and the clock control for the pe-
riodic interrupt timer.
Figure 5-9 Periodic Interrupt Timer and Software Watchdog Timer
5.4.6 Periodic Interrupt Timer
The periodic interrupt timer (PIT) allows the generation of interrupts of specific priority
at predetermined intervals. This capability is often used to schedule control system
tasks that must be performed within time constraints. The timer consists of a prescaler,
a modulus counter, and registers that determine interrupt timing, priority and vector as-
signment. Refer to
for further information about interrupt exception
processing.
Table 5-10 Software Watchdog Divide Ratio
SWP
SWT[1:0]
Divide Ratio
0
00
2
9
0
01
2
11
0
10
2
13
0
11
2
15
1
00
2
18
1
01
2
20
1
10
2
22
1
11
2
24
FREEZE
EXTAL
CRYSTAL
OSCILLATOR
128
1
XTAL
MODCLK
2
9
PRESCALER
CLOCK
SELECT
CLOCK SELECT
AND DISABLE
SWP
PTP
4
(8-BIT MODULUS COUNTER)
PIT
INTERRUPT
(2
15
DIVIDER CHAIN — 4 TAPS)
PERIODIC INTERRUPT TIMER
PICR
PITR
SOFTWARE WATCHDOG TIMER
SWSR
LPSTOP
SWE
SWT1
SWT0
SOFTWARE
WATCHDOG
RESET
PIT WATCHDOG BLOCK 16
NOTES:
1.
÷
128 IS PRESENT ONLY ON DEVICES WITH A FAST REFERENCE OSCILLATOR.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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