Lab X1 and 16F877 examples for beginners

[Demon]

Here's an external interrupt example using DT's Interrupts:

'********************************************************************
'*  Name     : LAB X1 External Interrupt.BAS  Version : 1.0         *
'*  Author   : Demon                   Date    : 2012-01-06  *
'*  Task     : External interrupt from keypad using DT Interrupts   *
'*  Hardware : PIC 16F877, 20mhz crystal                            *
'*           : Lab X1 Experimental Board                            *
'*           : MeLabs U2 Programmer v4.32                           *
'*  Software : PIC Basic Pro v2.60C                                 *
'*           : MicroCode Studio Plus v2.2.1.1                       *
'*           : MPASM Assembler v3.50                                *
'********************************************************************
'DEFINE  LOADER_USED 1

' Comment out CONFIG in MPASM include (File: 16F877.INC in PBP folder).
@ __config _HS_OSC & _WDT_OFF & _PWRTE_ON & _BODEN_ON & _LVP_OFF & _CPD_OFF & _WRT_ENABLE_OFF & _DEBUG_OFF
DEFINE  OSC 20

' Using only 4 bit bus to control LCD

DEFINE  LCD_DREG      PORTD         ' Set LCD data port
DEFINE  LCD_DBIT      4             ' Set starting data bit
DEFINE  LCD_RSREG     PORTE         ' Set LCD register select port
DEFINE  LCD_RSBIT     0             ' Set LCD register select bit
DEFINE  LCD_EREG      PORTE         ' Set LCD enable port
DEFINE  LCD_EBIT      1             ' Set LCD enable bit
DEFINE  LCD_BITS      4             ' Set LCD bus size
DEFINE  LCD_LINES     2             ' Set number of lines on LCD
DEFINE  LCD_COMMANDUS 2000          ' Set command delay time in microseconds
DEFINE  LCD_DATAUS    50            ' Set data delay time in microseconds

    TRISB = %00001111               ' Set port B pins to 4 output, 4 input
                                    ' B0 = External Interrupt
    TRISD = %00000000               ' Set all port D pins to output
    TRISE = %00000000               ' Set all port E pins to output

    ADCON1 = 7                      ' A/D off, all digital
    OPTION_REG.6 = 0                ' Sets interrupt trigger on falling edge
    OPTION_REG.7 = 0                ' Enable weak pull-up resistors

wsave   VAR BYTE    $70 SYSTEM      ' Required by Instant Interrupt routine
LED1    VAR     PORTD.0

    PAUSE   1000                    ' Wait for LCD to initalize
    LCDOUT  $FE,1,"LabX1 16F877 Ext Int"
    LCDOUT  $FE,$C0,"Any button on row 1"

    PORTD = %00000000               ' Clear LEDs

'---[INT - interrupt includes]--------------------------------------------------
INCLUDE "DT_INTS-14.bas"        ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"        ; Include if using PBP interrupts

'---[INT - interrupt definition]------------------------------------------------
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE                  ; Creates the interrupt processor
ENDASM

@   INT_ENABLE   INT_INT        ; enable external (INT) interrupts

Main:

    PORTB = %00000000               ' Set output on keypad
                                    '   to prevent floating pins
    GOTO Main

'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:
    TOGGLE LED1
@ INT_RETURN

    end

This is what it looks like on the Saleae Logic Analyser after 4 button presses: