MC68332ACFC25 Freescale Semiconductor, MC68332ACFC25 Datasheet - Page 47

• Manufacturer Part Number: MC68332ACFC25
• Description: IC MCU 32BIT 25MHZ 132-PQFP
• Manufacturer: Freescale Semiconductor
• Series: M683xxr

Specifications of MC68332ACFC25

• Core Processor: CPU32
• Core Size: 32-Bit
• Speed: 25MHz
• Connectivity: EBI/EMI, SCI, SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 15
• Program Memory Type: ROMless
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 132-QFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Program Memory Size: -
• Data Converters: -

4.2.11 Periodic Interrupt Timer
MC68332
USER’S MANUAL
LPSTOP
FREEZE
EXTAL
SWT0
SWT1
SWP
SWE
PTP
The periodic interrupt timer allows the generation of interrupts of specific priority at pre-
determined 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 SECTION 5 CENTRAL PROCESSING UNIT for further information
about interrupt exception processing.
The periodic interrupt modulus counter is clocked by a signal derived from the buffered
crystal oscillator (EXTAL) input pin unless an external frequency source is used. The
value of the periodic timer prescaler (PTP) bit in the periodic interrupt timer register
(PITR) determines system clock prescaling for the watchdog timer. One of two op-
tions, either no prescaling, or prescaling by a factor of 512, can be selected. The value
of PTP is affected by the state of the MODCLK pin during reset, as shown in Table 4-
5. System software can change PTP value.
Either clock signal (EXTAL or EXTAL
ulus counter (PITCLK). The modulus counter is initialized by writing a value to the pe-
riodic timer modulus (PITM) field in the PITR. A zero value turns off the periodic timer.
When the modulus counter value reaches zero, an interrupt is generated. The modu-
lus counter is then reloaded with the value in PITM and counting repeats. If a new val-
ue is written to PITR, it is loaded into the modulus counter when the current count is
completed.
Figure 4-3 Periodic Interrupt Timer and Software Watchdog Timer
DISABLE
CLOCK
Freescale Semiconductor, Inc.
PRESCALER (2
For More Information On This Product,
SYSTEM INTEGRATION MODULE
0 (External Clock)
Table 4-5 MODCLK Pin and
1 (Internal Clock)
MODCLK
Go to: www.freescale.com
9
)
PTP Bit at Reset
PRECLK
512) is divided by four before driving the mod-
CLOCK
MUX
1 ( 512)
SWCLK
0 ( 1)
4
PTP
PITCLK
2
9
DIVIDER CHAIN (2
8-BIT MODULUS
COUNTER
15 STAGE
2
11
PITR
2
13
15
)
2
15
PIT
INTERRUPT
RESET
PIT BLOCK
4-7