PIC16F871T-I/PT Microchip Technology, PIC16F871T-I/PT Datasheet - Page 100

• Manufacturer Part Number: PIC16F871T-I/PT
• Description: IC MCU FLASH 2KX14 EE 44TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F871T-I/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 33
• Program Memory Size: 3.5KB (2K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 64 x 8
• Ram Size: 128 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
• Package / Case: 44-TQFP, 44-VQFP
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 128 B
• Interface Type: PSP, USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 33
• Number Of Timers: 8
• 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
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 28 bit
• For Use With: I3-DB16F871 - BOARD DAUGHTER ICEPIC3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PIC16F870/871
11.11 Context Saving During Interrupts
During an interrupt, only the return PC value is saved
on the stack. Typically, users may wish to save key reg-
isters during an interrupt, (i.e., W register and STATUS
register). This will have to be implemented in software.
For the PIC16F870/871 devices, the register W_TEMP
must be defined in both banks 0 and 1 and must be
defined at the same offset from the bank base address
(i.e., If W_TEMP is defined at 0x20 in bank 0, it must
also be defined at 0xA0 in bank 1). The registers,
PCLATH_TEMP and STATUS_TEMP, are only defined
in bank 0.
EXAMPLE 11-1:
DS30569B-page 98
MOVWF
SWAPF
CLRF
MOVWF
MOVF
MOVWF
CLRF
:
:(ISR)
:
MOVF
MOVWF
SWAPF
MOVWF
SWAPF
SWAPF
W_TEMP
STATUS,W
STATUS
STATUS_TEMP
PCLATH, W
PCLATH_TEMP
PCLATH
PCLATH_TEMP, W
PCLATH
STATUS_TEMP,W
STATUS
W_TEMP,F
W_TEMP,W
SAVING STATUS, W, AND PCLATH REGISTERS IN RAM
;Copy W to TEMP register
;Swap status to be saved into W
;bank 0, regardless of current bank, Clears IRP,RP1,RP0
;Save status to bank zero STATUS_TEMP register
;Only required if using pages 1, 2 and/or 3
;Save PCLATH into W
;Page zero, regardless of current page
;(Insert user code here)
;Restore PCLATH
;Move W into PCLATH
;Swap STATUS_TEMP register into W
;(sets bank to original state)
;Move W into STATUS register
;Swap W_TEMP
;Swap W_TEMP into W
Since the upper 16 bytes of each bank are common in
the PIC16F870/871 devices, temporary holding regis-
ters W_TEMP, STATUS_TEMP, and PCLATH_TEMP
should be placed in here. These 16 locations don’t
require banking and therefore, make it easier for con-
text save and restore. The same code shown in
Example 11-1 can be used.
 2003 Microchip Technology Inc.