C8051T635-GM Silicon Laboratories Inc, C8051T635-GM Datasheet - Page 203

• Manufacturer Part Number: C8051T635-GM
• Description: IC MCU 2KB 20PIN QFN
• Manufacturer: Silicon Laboratories Inc
• Series: C8051T63xr

Specifications of C8051T635-GM

• Program Memory Type: OTP
• Program Memory Size: 2KB (2K x 8)
• Package / Case: 20-QFN
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 17
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 3.6 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: C8051T6x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 768 B
• Interface Type: I2C/SPI/UART
• Maximum Clock Frequency: 25 MHz
• Number Of Programmable I/os: 17
• Number Of Timers: 4
• Operating Supply Voltage: 1.8 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051T630DK
• Minimum Operating Temperature: - 40 C
• Package: 20QFN EP
• Device Core: 8051
• Family Name: C8051T63x
• Maximum Speed: 25 MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 336-1464 - KIT DEV FOR C8051T630 FAMILY
• Eeprom Size: -
• Data Converters: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1463-5

The 8-bit offset held in PCA0CPH2 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 off-
set is then given (in PCA clocks) by Equation 25.5, 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 PCA0CPH2 and
PCA0H. Software may force a WDT reset by writing a 1 to the CCF2 flag (PCA0CN.2) while the WDT is
enabled.
25.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:
1. Disable the WDT by writing a 0 to the WDTE bit.
2. Select the desired PCA clock source (with the CPS2–CPS0 bits).
3. Load PCA0CPL2 with the desired WDT update offset value.
4. Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle
5. Enable the WDT by setting the WDTE bit to 1.
6. Reset the WDT timer by writing to PCA0CPH2.
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 PCA0CPL2 defaults to 0x00. Using Equation 25.5, this results in a WDT
timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table 25.3 lists some example tim-
eout intervals for typical system clocks.
mode).
Equation 25.5. Watchdog Timer Offset in PCA Clocks
Notes:
System Clock (Hz)
1. Assumes SYSCLK/12 as the PCA clock source, and a PCA0L value
2. Internal SYSCLK reset frequency = Internal Oscillator divided by 8.
Table 25.3. Watchdog Timer Timeout Intervals
Offset
24,500,000
24,500,000
24,500,000
of 0x00 at the update time.
3,062,500
3,062,500
3,062,500
32,000
32,000
32,000
=
2
2
2

256 PCA0CPL2

PCA0CPL2
Rev. 1.0
255
128
255
128
255
128
32
32
32

+

256 PCA0L
C8051T630/1/2/3/4/5
Timeout Interval (ms)
–
24576
12384
129.5
3168
32.1
16.2
33.1
257
4.1

1
203