AT89LP51ED2-20AAU Atmel, AT89LP51ED2-20AAU Datasheet - Page 107

• Manufacturer Part Number: AT89LP51ED2-20AAU
• Description: 8-bit Microcontrollers - MCU 64KB 20MHz 2.4V-5.5V
• Manufacturer: Atmel

Specifications of AT89LP51ED2-20AAU

• Rohs: yes
• Core: 8051
• Processor Series: AT89x
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 20 MHz
• Program Memory Size: 64 KB
• Data Ram Size: 256 B
• On-chip Adc: Yes
• Operating Supply Voltage: 2.4 V to 5.5 V
• Operating Temperature Range: - 40 C to + 85 C
• Package / Case: LQFP-44
• Mounting Style: SMD/SMT
• Data Rom Size: 4 KB
• Interface Type: 2-Wire, SPI, UART
• Number Of Programmable I/os: 36
• Number Of Timers: 3
• Program Memory Type: Flash
• Factory Pack Quantity: 160

16.1
3714A–MICRO–7/11
Software Reset
The program sequence to feed or enable the watchdog timer is as follows:
Table 16-1.
The WDT time-out period is dependent on the system clock frequency.
A Software Reset of the AT89LP51RD2/ED2/ID2 is accomplished by writing the software reset
sequence 5AH/A5H to the WDTRST SFR. The WDT does not need to be enabled to generate
the software reset. A normal software reset will set the SWRST flag in WDTCON. However, if at
any time an incorrect sequence is written to WDTRST (i.e. anything other than 1EH/E1H or
5AH/A5H), a software reset will immediately be generated and both the SWRST and WDTOVF
flags will be set. In this manner an intentional software reset may be distinguished from a soft-
ware error-generated reset. The program sequence to generate a software reset is as follows:
A software reset has the same duration as the normal watchdog reset and will also generate a
reset pulse on the RST pin unless DISRTO is set.
WTO2
0
0
0
0
1
1
1
1
MOV WDTRST, #01Eh
MOV WDTRST, #0E1h
MOV WDTRST, #05Ah
MOV WDTRST, #0A5h
Watchdog Timer Time-out Period Selection
WDT Prescaler Bits
WTO1
0
0
1
1
0
0
1
1
AT89LP51RD2/ED2/ID2 Preliminary
WTO0
0
1
0
1
0
1
0
1
1024K x (TPS+1)
2048K x (TPS+1)
128K x (TPS+1)
256K x (TPS+1)
512K x (TPS+1)
(Clock Cycles)
16K x (TPS+1)
32K x (TPS+1)
64K x (TPS+1)
Period
()
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