AT89C51IC2-RLTIL Atmel, AT89C51IC2-RLTIL Datasheet - Page 46

IC 8051 MCU FLASH 32K 44VQFP

AT89C51IC2-RLTIL

Manufacturer Part Number
AT89C51IC2-RLTIL
Description
IC 8051 MCU FLASH 32K 44VQFP
Manufacturer
Atmel
Series
89Cr
Datasheet

Specifications of AT89C51IC2-RLTIL

Core Processor
8051
Core Size
8-Bit
Speed
40MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
POR, PWM, WDT
Number Of I /o
34
Program Memory Size
32KB (32K x 8)
Program Memory Type
FLASH
Ram Size
1.25K x 8
Voltage - Supply (vcc/vdd)
2.7 V ~ 3.6 V
Oscillator Type
External
Operating Temperature
-40°C ~ 85°C
Package / Case
44-TQFP, 44-VQFP
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Eeprom Size
-
Data Converters
-

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PCA Watchdog Timer
46
AT89C51IC2
Figure 16. 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 14 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:
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.
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.
ECOMn
CAPPn
Enable
CAPNn MATn TOGn PWMn ECCFn
Overflow
PCA counter/timer
8 bit comparator
CCAPnH
CCAPnL
CL
CCAPMn, n= 0 to 4
0xDA to 0xDE
“1”
“0”
4301D–8051–02/08
CEXn

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