Ronald Cotton says:
What is wrong with the following code? It is supposed created a 2 sec delay; however, when I simulate the code in MPLAB version 5.2, the code causes the program to lock up around 65ms or so.I can successfully generate a 0.5 second delay by changing PostScaler value to 4 instead of 16.
When I program the 2 second delay program into the PIC, the LEDs that I have to PORTB stay on; however, when I program the 0.5 second delay into the chip, the LEDs on PORTB blink every 0.5 seconds.
;********************************************************************** ; This file is a basic code template for assembly code generation * ; on the PICmicro PIC16C74A. This file contains the basic code * ; building blocks to build upon. * ; * ; If interrupts are not used all code presented between the ORG * ; 0x004 directive and the label main can be removed. In addition * ; the variable assignments for 'w_temp' and 'status_temp' can * ; be removed. * ; * ; Refer to the MPASM User's Guide for additional information on * ; features of the assembler (Document DS33014). * ; * ; Refer to the respective PICmicro data sheet for additional * ; information on the instruction set. * ; * ; Template file assembled with MPLAB V3.99.18 and MPASM V2.15.06. * ; * ;********************************************************************** ; * ; Filename: 4720Lab2.asm * ; Date: 01/24/2001 * ; File Version: 1 * ; * ; Author: Ronald J Cotton * ; Company: * ; * ; * ;********************************************************************** ; * ; Files required: * ; * ; * ; * ;********************************************************************** ; * ; Notes: * ; * ; * ; * ; * ;********************************************************************** list p=16c74b ; list directive to define processor #include <p16c74b.inc> ; processor specific variable definitions __CONFIG _CP_OFF & _WDT_ON & _BODEN_ON & _PWRTE_ON & _XT_OSC ; '__CONFIG' directive is used to embed configuration data within .asm file. ; The lables following the directive are located in the respective .inc file. ; See respective data sheet for additional information on configuration word. ;***** VARIABLE DEFINITIONS w_temp EQU 0x20 ; variable used for context saving status_temp EQU 0x21 ; variable used for context saving Channel EQU 0X22 ; Channel Variable Counter EQU 0X23 ; Counter DelayValue EQU 0x24 ; Delay Info EQU 0x25 DelayTemp EQU 0x26 ; variable used for context saving cblock 0x27 ; Beginning unused RAM AdValue:8 ; endc ;********************************************************************** ORG 0x000 ; processor reset vector clrf PCLATH ; ensure page bits are claared goto main ; go to beginning of program ORG 0x004 ; interrupt vector location movwf w_temp ; save off current W register contents movf STATUS,w ; move status register into W register bcf STATUS,RP0 ; ensure file register bank set to 0 movwf status_temp ; save off contents of STATUS register movf DelayValue,w ; move status register into W register movwf DelayTemp ; save off current DelayValue contents btfsc PIR1,TMR2IF ; Handler for Timer2 call IntTimer2 ; Interrupt Handler for Timer2 bcf STATUS,RP0 ; ensure file register bank set to 0 movf status_temp,w ; retrieve copy of STATUS register movwf STATUS ; restore pre-isr STATUS register contents movf DelayTemp,W ; retrieve copy of delay register movwf DelayValue ; restore pre-isr DelayValue register swapf w_temp,f swapf w_temp,w ; restore pre-isr W register contents retfie ; return from interrupt IntTimer2: bcf PIR1,TMR2IF ; Must Clear Int flag for Timer2 decf Counter,F ; Decrease Counter return main: bcf STATUS,RP0 ; movlw 0x31 ; movwf Counter ; call InitTimer2 ; movlw 0xc0 ; movwf INTCON ; movlw 0x4A ; Prescaler=16, PostScaler=16 movwf T2CON ; Since OSC = 4Mhz timer = 1uS bsf T2CON,TMR2ON ; Start Timer MainLoop: call FiveSec call LED goto MainLoop ;********************************************************************************************* ;* Everything in this section represents either initialization code or * ;* helper functions. * ;* * ;* Ronald J.Cotton * ;* 02/02/2001 * ;********************************************************************************************* FiveSec: btfss Counter,7 ; goto FiveSec movlw 0x32 ; addwf Counter,F ; Put Counter back to 50 return LED: comf PORTB ; Toggle PORTB return InitTimer2: bcf STATUS,RP0 ; Ensure Reg Bank 0 clrf T2CON ; Stop Timer2, Pre=1:1, Post=1:1 clrf TMR2 ; Clear Timer2 register clrf PIR1 ; Clear Interrupt Flag register bsf STATUS,RP0 ; Bank1 clrf PIE1 ; Disable all Peripheral Interrupts bsf PIE1,TMR2IE ; Enable only Timer2 movlw 0xf9 ; Timeout Value = 249 movwf PR2 ; clrf TRISB ; Make PortB output bcf STATUS,RP0 ; Back to Bank0 movlw 0xff ; All on movwf PORTB ; Initialize LEDS to be on return END ; directive 'end of program'
Scott Lee Says:
I see _WDT_ON in the config but there are no clrwdt instructions so I'm sure that is a problem when you try to use the 2 second delay on real HW.+
As for MPLAB simulation, yes it seems to pause the execution after some short (in human terms) period of execution. In my experience it isn't reseting the device or anything -- it's like it just decides to insert a break point.
Questions:
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