PIC16F877-20/P Microchip Technology, PIC16F877-20/P Datasheet - Page 98

• Manufacturer Part Number: PIC16F877-20/P
• Description: IC MCU FLASH 8KX14 EE 40DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F877-20/P

• Core Size: 8-Bit
• Program Memory Size: 14KB (8K x 14)
• Core Processor: PIC
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 33
• Program Memory Type: FLASH
• 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: 0°C ~ 70°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Controller Family/series: PIC16F
• No. Of I/o's: 33
• Eeprom Memory Size: 256Byte
• Ram Memory Size: 368Byte
• Cpu Speed: 20MHz
• No. Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 444-1001 - DEMO BOARD FOR PICMICRO MCU
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

PICmicro MID-RANGE MCU FAMILY
6.2.1
6.2.2
6.2.3
DS31006A-page 6-4
Reset Vector
Interrupt Vector
Calibration Information
On any device, a reset forces the Program Counter (PC) to address 0h. We call this address the
“Reset Vector Address” since this is the address that program execution will branch to when a
device reset occurs.
Any reset will also clear the contents of the PCLATH register. This means that any branch at the
Reset Vector Address (0h) will jump to that location in PAGE0 of the program memory.
When an interrupt is acknowledged the PC is forced to address 0004h. We call this the “Interrupt
Vector Address”. When the PC is forced to the interrupt vector, the PCLATH register is not mod-
ified. Once in the service interrupt routine (ISR), this means that before any write to the PC, the
PCLATH register should be written with the value that will specify the desired location in program
memory. Before the PCLATH register is modified by the Interrupt Service Routine (ISR) the con-
tents of the PCLATH may need to be saved, so it can be restored before returning from the ISR.
Some devices have calibration information stored in their program memory. This information is
programmed by Microchip when the device is under final test. The use of these values allows the
application to achieve better results. The calibration information is typically at the end of program
memory, and is implemented as a RETLW instruction with the literal value being the specified cal-
ibration information.
Note:
For windowed devices, write down all calibration values BEFORE erasing. This
allows the device’s calibration values to be restored when the device is re-pro-
grammed. When possible writing the values on the package is recommended.
1997 Microchip Technology Inc.