PIC Microcontoller Input / Output LED Methods

Tony Nixon [sales at picnpoke.com] of ICmicro's says:

This program will flash a LED from port pin RC4

RC4 -> Led Anode
Led Cathode -> 1K res
1K res -> ground
;
 Title "LED flasher."
;
 list P = 16F877
;
 include "P16f877.inc" ; use definition file for 16F877
;
; --------------------
; USER RAM DEFINITIONS
; --------------------
;
 CBLOCK 0x20 ; RAM starts at address 20h
NaHi
NaLo
NbHi
NbLo
 ENDC
;
 org 0x0000 ; start address = 0000h
; INITIALISE PORTS
; binary used to see individual pin level
 movlw b'00000000' ; all port pins = low
 movwf PORTA
 movlw b'00000000'
 movwf PORTB
 movlw b'00000000'
 movwf PORTC
 movlw b'00000000'
 movwf PORTD
 movlw b'00000000'
 movwf PORTE
 bsf STATUS,RP0 ; set RAM Page 1 for TRIS registers
; INITIALISE PORTS
; binary used to see individual pin IO status
 movlw b'00000000' ; all IO pins = outputs
 movwf TRISA
 movlw b'00000000'
 movwf TRISB
 movlw b'00000000'
 movwf TRISC
 movlw b'00000000'
 movwf TRISD
 movlw b'00000000'
 movwf TRISE
 movlw b'00000110' ; all analog pins = digital
 movwf ADCON1
 bcf STATUS,RP0 ; back to RAM page 0
; LED FLASH LOOP
Loop bsf PORTC,4 ; RC4 = high = led on
 call Delay
 bcf PORTC,4 ; RC4 = low = led off
 call Delay
 goto Loop
; 1/2 SEC DELAY SUBROUTINE WITH 4MHz CLOCK
Delay movlw 01h
 movwf NbHi
 movlw 03h
 movwf NbLo
 movlw 8Ah
 movwf NaHi
 movlw 5Bh
 movwf NaLo
DeLoop0 decfsz NaLo,F
 goto DeLoop0
 decfsz NaHi,F
 goto DeLoop0
 decfsz NbLo,F
 goto DeLoop0
 decfsz NbHi,F
 goto DeLoop0
 ;
 return
 end

Questions:

• spamgav_28TakeThisOuT at SPAMhotmail.com asks:

  Hi, i too am new to programming pics. im trying to program the PIC16F877 to be a realtime clock and to output the time on an LCD display (pref 4 bit to the LCD) if anyone has code or knows where i can find an exmaple of a real time clock i would be so grateful. Im using MPlab to program so assmelby language rather than C or Basic, many thanks

• spamtigrotTakeThisOuT at SPAMonvol.net asks:

  hi!
  i am a newbie in programming pics,the only pic that i have programmed is the 16F84.now i wish to move to a greater stuff - pic 16F877.Can someone PLEASE send me some good tutorial sites?
  
  Thank You
  

  James Newton replies: See piclist.com/techref/microchip/begin.htm+

  +

• spambranvan2kTakeThisOuT at SPAMyahoo.es asks:

  i'm a beginner in pic's programming, i say so because my question may sound silly, but here it comes, which electronics i need to make it up? Do you have the design?

  Check the data sheet for the processor clock and power, then just add a 1Kohm resistor and LED between the IO pin to ground.

Comments:

• BE AWARE !!!
  
  There is a mistake in the code. It should be "org 0x0020" instead of "org 0x0000". The way it is now it will not even build.
  
  Daniel+
• spamlivewireTakeThisOuT at SPAMtelusplanet.net

  Found a formula to apply your delay routine to. It may not be 100% accurate, but it is really close. (12/Clock Frequency) = Delay/Steps Where steps are offset by 1. Such that 16Mhz clock would provide a delay of 750ms per step. If you required a delay of 500ms, you would need 666,666 steps. Convert 666,666 to Hex and you get 00 0A 2C 2A. Enter these values offset by 1, and you get NaHi=0x2D NaLo=0x2B NbHi=0x01 NbLo=0x0B Works for me.

  +

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