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
I'm using MPLAB 8.46 and only the TMR0L is incrementing. ???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
Posted by PickyBiker
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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..
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