MC68332ACFC25 Freescale Semiconductor, MC68332ACFC25 Datasheet - Page 46

• 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: -

4-6
Perform a software watchdog service sequence as follows:
Both writes must occur before time-out in the order listed, but any number of instruc-
tions can be executed between the two writes.
Watchdog clock rate is affected by the software watchdog prescale (SWP) and soft-
ware watchdog timing (SWT) fields in SYPCR.
SWP determines system clock prescaling for the watchdog timer and determines that
one of two options, either no prescaling or prescaling by a factor of 512, can be select-
ed. The value of SWP is affected by the state of the MODCLK pin during reset, as
shown in Table 4-3. System software can change SWP value.
The SWT field selects the divide ratio used to establish software watchdog time-out
period. Time-out period is given by the following equations.
Table 4-4 shows the ratio for each combination of SWP and SWT bits. When SWT[1:0]
are modified, a watchdog service sequence must be performed before the new time-
out period can take effect.
Figure 4-3 is a block diagram of the watchdog timer and the clock control for the pe-
riodic interrupt timer.
1. Write $55 to SWSR.
2. Write $AA to SWSR.
Time-out Period
Freescale Semiconductor, Inc.
Table 4-4 Software Watchdog Ratio
For More Information On This Product,
Time-out Period
SWP
SYSTEM INTEGRATION MODULE
0 (External Clock)
Table 4-3 MODCLK Pin and
1 (Internal Clock)
0
0
0
0
1
1
1
1
MODCLK
SWP Bit During Reset
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=
------------------------------------------------------------------------------------ -
EXTAL Frequency Divide Ratio
SWT
00
01
10
11
00
01
10
11
=
------------------------------------------------ -
EXTAL Frequency
or
Divide Ratio
1 ( 512)
0 ( 1)
SWP
1
Ratio
2
2
2
2
2
2
2
2
11
13
15
18
20
22
24
9
USER’S MANUAL
MC68332