C8051F544-IM Silicon Laboratories Inc, C8051F544-IM Datasheet - Page 261

• Manufacturer Part Number: C8051F544-IM
• Description: IC 8051 MCU 8K FLASH 32-QFN
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F54xr

Specifications of C8051F544-IM

• Program Memory Type: FLASH
• Program Memory Size: 8KB (8K x 8)
• Package / Case: 32-QFN
• Mfg Application Notes: LIN Bootloader AppNote
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 50MHz
• Connectivity: SMBus (2-Wire/I²C), LIN, SPI, UART/USART
• Peripherals: POR, PWM, Temp Sensor, WDT
• Number Of I /o: 25
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.25 V
• Data Converters: A/D 25x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Processor Series: C8051F5x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Maximum Clock Frequency: 50 MHz
• Number Of Programmable I/os: 25
• Operating Supply Voltage: 1.8 V to 5.25 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051F540DK
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 336-1672 - BOARD PROTOTYPE W/C8051F540336-1669 - KIT DEVELOPMENT FOR C8051F540
• Eeprom Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1677-5

Note that the 8-bit offset held in PCA0CPH5 is compared to the upper byte of the 16-bit PCA counter. This
offset value is the number of PCA0L overflows before a reset. Up to 256 PCA clocks may pass before the
first PCA0L overflow occurs, depending on the value of the PCA0L when the update is performed. The
total offset is then given (in PCA clocks) by Equation 24.5, where PCA0L is the value of the PCA0L register
at the time of the update.
The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH5 and
PCA0H. Software may force a WDT reset by writing a 1 to the CCF5 flag (PCA0CN.5) while the WDT is
enabled.
24.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:






The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog
timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the
WDT cannot be disabled until the next system reset. If WDLCK is not set, the WDT is disabled by clearing
the WDTE bit.
The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by
12, PCA0L defaults to 0x00, and PCA0CPL5 defaults to 0x00. Using Equation 24.5, this results in a WDT
timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table 24.3 lists some example time-
out intervals for typical system clocks.
Disable the WDT by writing a 0 to the WDTE bit.
Select the desired PCA clock source (with the CPS[2:0] bits).
Load PCA0CPL5 with the desired WDT update offset value.
Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle
mode).
Enable the WDT by setting the WDTE bit to 1.
Reset the WDT timer by writing to PCA0CPH5.
PCA0CPL5
C
D
L
I
W
D
T
E
PCA0MD
W
D
C
K
L
PCA0CPH2
C
P
S
2
Figure 24.11. PCA Module 2 with Watchdog Timer Enabled
Write to
C
P
S
1
C
P
S
0
Equation 24.5. Watchdog Timer Offset in PCA Clocks
E
C
F
Offset
8-bit Adder
=
Enable
Adder

256
x
Enable
PCA0CPL5
Rev. 1.1
PCA0CPH5
Comparator
PCA0H
8-bit

+

256 PCA0L
–
Match
PCA0L Overflow

C8051F54x
Reset
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