MC68HC16Z1CPV16 Datasheet, PDF (133/500 Pages) Freescale Semiconductor, Inc – Symbols and Operators, CPU16 Register Mnemonics

Freescale Semiconductor, Inc.
Table 5-10 Software Watchdog Divide Ratio
SWP
0
0
0
0
1
1
1
1
SWT[1:0]
00
01
10
11
00
01
10
11
Divide Ratio
2⁹
2¹¹
2¹³
2¹⁵
2¹⁸
2²⁰
2²²
2²⁴
Figure 5-9 is a block diagram of the watchdog timer and the clock control for the pe-
riodic interrupt timer.
EXTAL XTAL
FREEZE MODCLK
CRYSTAL
OSCILLATOR
128¹
CLOCK SELECT
AND DISABLE
2⁹ PRESCALER
SWP
CLOCK
SELECT
PTP
4
SOFTWARE
WATCHDOG
RESET
LPSTOP
SWE
SWT1
SWT0
SOFTWARE WATCHDOG TIMER
(2¹⁵ DIVIDER CHAIN — 4 TAPS)
SWSR
PERIODIC INTERRUPT TIMER
(8-BIT MODULUS COUNTER)
PICR
PITR
PIT
INTERRUPT
NOTES:
1. ÷ 128 IS PRESENT ONLY ON DEVICES WITH A FAST REFERENCE OSCILLATOR.
PIT WATCHDOG BLOCK 16
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 4.13 Exceptions for further information about interrupt exception
processing.
M68HC16 Z SERIES
USER’S MANUAL
SYSTEM INTEGRATION MODULE
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