PIC18f2620 Timer0 in 16-bit mode
It's been a while since I posted anything here because since the last post I rode my motorcycle from Austin, TX to Burlington, ME and back and had a 2 week vacation in Finland, Norway, and Sweden. After a 3-week recovery, I am back to PIC programming.
I'm having trouble with the 16-bit mode of timer0 in a PIC18f2620. I don't seem to be able to get TMR0H to change. Basically I'm trying to get it to count from 0 to 65535 in about 26.2 MS, but TMR0H never seems to change. Here's the code
Code:
;**********************************************************************
; Files Required: P18F2620.INC *
;**********************************************************************
; Notes: Future version will incorporate *
; 1) Low battery detector to start a flashing warning when the *
; voltage drops below 3v/cell for LIPO's *
; 2) A digital compass so the quadracopter has a sense of *
; direction. *
; 3) A GPS so the quadracopter is capable of moving to specific *
; coordinates. *
;**********************************************************************
errorlevel -302 ; wrong bank warning
LIST P=18F2620 ;directive to define processor
#include
;processor specific variable definitions
CONFIG WDT=OFF ; disable watchdog timer
CONFIG MCLRE = ON ; MCLEAR Pin on
CONFIG DEBUG = OFF ; Disable Debug Mode / RB6-7 are I/O pins
CONFIG LVP = OFF ; Low-Voltage programming disabled (necessary for debugging)
CONFIG OSC = HSPLL
CBLOCK 0x080
WREG_TEMP ;variable used for context saving
STATUS_TEMP ;variable used for context saving
BSR_TEMP ;variable used for context saving
ENDC
;*****************************************************************************************
; DEFINES VARIABLES *
;*****************************************************************************************
; PORTA definitions
#define FRONT PORTA,0 ; Front servo output
#define BACK PORTA,1
#define LEFT PORTA,2
#define RIGHT PORTA,3
; define input pulses
#define AILERON rb_read,4 ; Aileron input
#define ELEVATOR rb_read,5
#define THROTTLE rb_read,6
#define RUDDER rb_read,7
#define RUDDER_PULSE FLAGS,0
#define IN_OUTPUT FLAGS,1
udata
w_temp res 1 ; variable used for context saving
status_temp res 1 ; variable used for context saving
pclath_temp res 1 ; variable used for context saving
FLAGS res 1 ; just a byte for various flags
rb_read res 1 ; storage loc for the inputs
aileron_high_l res 1 ; timer0 low byte
aileron_high_h res 1 ; timer0 high byte
aileron_low_l res 1
aileron_low_h res 1
throttle_high_l res 1 ; timer0 low byte
throttle_high_h res 1 ; timer0 high byte
throttle_low_l res 1
throttle_low_h res 1
elevator_high_l res 1 ; timer0 low byte
elevator_high_h res 1 ; timer0 high byte
elevator_low_l res 1
elevator_low_h res 1
rudder_high_l res 1 ; timer0 low byte
rudder_high_h res 1 ; timer0 high byte
rudder_low_l res 1
rudder_low_h res 1
code 0x0000
goto main ; Reset Vector, go to beginning of program
ORG 0x0008 ; high priority interrupt vector location
bra high_int ; high priority interrupt, goto high_int
ORG 0x0018 ; low priority interrupt vector
movff STATUS,STATUS_TEMP ; save STATUS register
movff WREG,WREG_TEMP ; save working register
movff BSR,BSR_TEMP ; save BSR register
call low_int
movff BSR_TEMP,BSR ;restore BSR register
movff WREG_TEMP,WREG ;restore working register
movff STATUS_TEMP,STATUS ;restore STATUS register
retfie
main:
clrf ADCON0 ; Turn off A/D converters
movlw 0x0F
movwf ADCON1 ; All pins are Digital I/O
movlw 0x07
movwf CMCON ; turn off the comparators
clrf TRISA ; all pins are outputs
movlw 0xF0
movwf TRISB ; 7:4 input, 3:0 outputs
clrf TRISC ; all outputs
clrf PORTA ; all zeros
clrf PORTB ; all zeros
clrf PORTC ; all zeros
; Set TMR0 to 16-bit mode, interrupt every 26.2ms & enable RB change
movlw B'10000001'
movwf T0CON ; timer0 enable, 16-bit, 1:4
movlw B'11101000'
movwf INTCON ; Global IE, Peripheral IE, TMR0 Overflow Int Enable, RB change
clrf INTCON2
movlw 0
movwf TMR0H
movwf TMR0L ; set the timer0 offset for 26.2ms
clrf CVRCON ; comparators off
clrf rb_read
clrf FLAGS
loop:
goto loop
high_int
btfsc INTCON, TMR0IF ; if TMR0IF is set, it's a clock interrupt
call clock_isr
btfsc INTCON, RBIF ; if RBIF is set, it's a data change interrupt
call data_isr
retfie FAST
low_int ; comes here on low priority interrupt
return
;********************************************************************************************************
clock_isr:
;********************************************************************************************************
; reset the timer0 to interrupt after 26.2ms
movlw 0 ; set timer for 26.2ms
; movwf TMR0H
movwf TMR0L
bcf INTCON, TMR0IF ; reset the timer0 interrupt flag
clock_exit
return ; return from interrupt
;********************************************************************************************************
data_isr:
;********************************************************************************************************
movf PORTB, w ; get 4 inputs (clear the mismatch)
bcf INTCON, RBIF ; clear the interrupt flag
movwf rb_read ; move w register to rb_read
return ; return from interrupt
END
I'm using MPLAB 8.46 and only the TMR0L is incrementing. ???
Posted by PickyBiker
===================
Posted by Bruce:
Place TMR0_Internal in the watch window VS TMR0H & TMROL. With MPSIM you sometimes need to place TMRx_Internal in the watch windows VS TMRxH since this is a shadow register on some, and doesn't update like normal.
Edit: Attempted to move this thread from the PBP section, and deleted by mistake, so re-posted relevant portions here. Sorry..;)
