TS80C51RA2-LIA Atmel, TS80C51RA2-LIA Datasheet - Page 33

• Manufacturer Part Number: TS80C51RA2-LIA
• Description: IC MCU 8BIT 256BYTE 30MHZ 44PLCC
• Manufacturer: Atmel
• Series: 80Cr

Specifications of TS80C51RA2-LIA

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 30/20MHz
• Connectivity: UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Type: ROMless
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-PLCC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Program Memory Size: -
• Data Converters: -

6.3.5
4188F–8051–01/08
PCA Watchdog Timer
Figure 6-9.
An on-board watchdog timer is available with the PCA to improve the reliability of the system
without increasing chip count. Watchdog timers are useful for systems that are susceptible to
noise, power glitches, or electrostatic discharge. Module 4 is the only PCA module that can be
programmed as a watchdog. However, this module can still be used for other modes if the
watchdog is not needed. Figure 6-7 shows a diagram of how the watchdog works. The user pre-
loads a 16-bit value in the compare registers. Just like the other compare modes, this 16-bit
value is compared to the PCA timer value. If a match is allowed to occur, an internal reset will be
generated. This will not cause the RST pin to be driven high.
In order to hold off the reset, the user has three options:
The first two options are more reliable because the watchdog timer is never disabled as in option
#3. If the program counter ever goes astray, a match will eventually occur and cause an internal
reset. The second option is also not recommended if other PCA modules are being used.
Remember, the PCA timer is the time base for all modules; changing the time base for other
modules would not be a good idea. Thus, in most applications the first solution is the best option.
This watchdog timer won’t generate a reset out on the reset pin.
• 1. Periodically change the compare value so it will never match the PCA timer,
• 2. periodically change the PCA timer value so it will never match the compare values, or
• 3. Disable the watchdog by clearing the WDTE bit before a match occurs and then re-enable
it.
ECOMn
PCA PWM Mode
CAPPn
Enable
CAPNn MATn TOGn PWMn ECCFn
Overflow
PCA counter/timer
8 bit comparator
CCAPnH
CCAPnL
CL
<
Š
CCAPMn, n= 0 to 4
0xDA to 0xDE
“1”
“0”
AT/TS8xC51Rx2
CEXn
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