PIC16F877A-I/L Microchip Technology, PIC16F877A-I/L Datasheet - Page 157

• Manufacturer Part Number: PIC16F877A-I/L
• Description: IC MCU FLASH 8KX14 EE 44PLCC
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F877A-I/L

• Program Memory Type: FLASH
• Program Memory Size: 14KB (8K x 14)
• Package / Case: 44-PLCC
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 33
• Eeprom Size: 256 x 8
• Ram Size: 368 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 368 B
• Interface Type: I2C/SPI/USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 33
• Number Of Timers: 3
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, DM163022, DV164120
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8-ch x 10-bit
• Package: 44PLCC
• Device Core: PIC
• Family Name: PIC16
• Maximum Speed: 20 MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC164309 - MODULE SKT FOR PM3 44PLCC444-1001 - DEMO BOARD FOR PICMICRO MCUDVA16XL441 - ADAPTER DEVICE ICE 44PLCC309-1040 - ADAPTER 44-PLCC ZIF TO 40-DIP309-1039 - ADAPTER 44-PLCC TO 40-DIPDV007003 - PROGRAMMER UNIVERSAL PROMATE II
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: PIC16F877AI/L

14.13 Watchdog Timer (WDT)
The Watchdog Timer is a free running, on-chip RC
oscillator which does not require any external
components. This RC oscillator is separate from the
RC oscillator of the OSC1/CLKI pin. That means that
the WDT will run even if the clock on the OSC1/CLKI
and OSC2/CLKO pins of the device has been stopped,
for example, by execution of a SLEEP instruction.
During normal operation, a WDT time-out generates a
device Reset (Watchdog Timer Reset). If the device is
in Sleep mode, a WDT time-out causes the device to
wake-up and continue with normal operation (Watch-
dog Timer Wake-up). The TO bit in the Status register
will be cleared upon a Watchdog Timer time-out.
The WDT can be permanently disabled by clearing
configuration bit, WDTE (Section 14.1 “Configuration
Bits”).
FIGURE 14-11:
TABLE 14-7:
 2003 Microchip Technology Inc.
2007h
81h, 181h
Legend: Shaded cells are not used by the Watchdog Timer.
Note 1:
Address
See Register 14-1 for operation of these bits.
Config. bits
OPTION_REG
Name
SUMMARY OF WATCHDOG TIMER REGISTERS
Note:
WDT Timer
Enable Bit
WDT
WATCHDOG TIMER BLOCK DIAGRAM
PSA and PS2:PS0 are bits in the OPTION_REG register.
From TMR0 Clock Source
(Figure 5-1)
RBPU
Bit 7
(1)
BODEN
INTEDG
0
1
Bit 6
PSA
M
U
X
(1)
T0CS
Bit 5
CP1
0
WDT time-out period values may be found in
Section 17.0 “Electrical Characteristics” under
parameter #31. Values for the WDT prescaler (actually
a postscaler but shared with the Timer0 prescaler) may
be assigned using the OPTION_REG register.
T0SE
Bit 4
CP0
Time-out
MUX
8-to-1 MUX
WDT
Note 1: The CLRWDT and SLEEP instructions
Postscaler
1
2: When a CLRWDT instruction is executed
8
PWRTE
Bit 3
clear the WDT and the postscaler, if
assigned to the WDT and prevent it from
timing out and generating a device Reset
condition.
and the prescaler is assigned to the WDT,
the prescaler count will be cleared but the
prescaler assignment is not changed.
PSA
PSA
To TMR0 (Figure 5-1)
(1)
PIC16F87XA
PS2:PS0
WDTE
Bit 2
PS2
F
Bit 1
DS39582B-page 155
PS1
OSC
1
F
Bit 0
PS0
OSC
0