T89C51RD2-SLSIM Atmel, T89C51RD2-SLSIM Datasheet - Page 32
T89C51RD2-SLSIM
Manufacturer Part Number
T89C51RD2-SLSIM
Description
IC MICRO CTRL 64K FLASH 44PLCC
Manufacturer
Atmel
Series
89Cr
Datasheet
1.T89C51RD2-SMSIM.pdf
(104 pages)
Specifications of T89C51RD2-SLSIM
Core Processor
8051
Core Size
8-Bit
Speed
40MHz
Connectivity
SPI, UART/USART
Peripherals
POR, PWM, WDT
Number Of I /o
32
Program Memory Size
64KB (64K x 8)
Program Memory Type
FLASH
Eeprom Size
2K x 8
Ram Size
1.25K x 8
Voltage - Supply (vcc/vdd)
4.5 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
Data Converters
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PCA Watchdog Timer
32
T89C51RD2
Figure 12. PCA PWM Mode
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 10 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 mod-
ules 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 appli-
cations 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
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”
4243G–8051–05/03
CEXn
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