mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 127

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5.4.6 Periodic Interrupt Timer
MC68HC16Y3/916Y3
USER’S MANUAL
EXTAL
OSCILLATOR
Figure 5-8 is a block diagram of the watchdog timer and the clock control for the
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
assignment. Refer to 4.13 Exceptions for further information about interrupt exception
processing.
CRYSTAL
NOTES:
1. 128 IS PRESENT ONLY ON DEVICES WITH A FAST REFERENCE OSCILLATOR.
XTAL
Figure 5-8 Periodic Interrupt Timer and Software Watchdog Timer
128
SWP
WATCHDOG
SOFTWARE
0
0
0
0
1
1
1
1
1
LPSTOP
RESET
SWT1
SWT0
Table 5-6 Software Watchdog Divide Ratio
SWE
FREEZE
Freescale Semiconductor, Inc.
CLOCK SELECT
AND DISABLE
For More Information On This Product,
MODCLK
SOFTWARE WATCHDOG TIMER
(2
Go to: www.freescale.com
15
SWT[1:0]
DIVIDER CHAIN — 4 TAPS)
00
01
10
11
00
01
10
11
2
9
PRESCALER
SWSR
PERIODIC INTERRUPT TIMER
Divide Ratio
(8-BIT MODULUS COUNTER)
PICR
2
2
2
2
2
2
2
SELECT
CLOCK
2
11
13
15
18
20
22
24
9
4
PITR
SWP
PTP
MOTOROLA
PIT WATCHDOG BLOCK 16
INTERRUPT
PIT
5-19