AVR-Chat

Here I am replying to my own message ...

Anyway, in re-reading what I wrote, I should have added that the vectors
must be "rjmp address", not just address as I put in the message. ( from my
Motorola assembler habits I guess. )

I wrote a simple version of the method below and it does work in the
simulator correctly.

Jim
----- Original Message ----- 
From: "James Hatley" <james.hatley@comcast.net>
To: <AVR-Chat@yahoogroups.com>
Sent: Wednesday, July 06, 2005 1:40 PM
Subject: Re: [AVR-Chat] Timer1 Problems


> Here is how I do timer startup ... (hope I got this correct...)
>
> initialization of timer
>
> ... stop interrupts (CLI)
> ... stop timer TCCR1B  = 0
> ... set for CTC etc in TCCR1A
> ... set OCR1A as required
> ... set TCNT as required
> ... start timer TCCR1B = 9 (or whatever required)
> ... set TIMSK as necessary
> ... enable interrupts (SEI)
>
> and maybe you just didn't include it but I think you must load your
> interrupt service routine (ISR) address into the appropriate interrupt
> vector and you must have an ISR routine.
>
> As I understand it the flag should be cleared when the program jumps to
that
> ISR address.
>
> Good Luck
>
> Jim
>
> ----- Original Message ----- 
> From: "Aaron" <aaron.groups@gmail.com>
> To: <avr-chat@yahoogroups.com>
> Sent: Wednesday, July 06, 2005 12:54 PM
> Subject: [AVR-Chat] Timer1 Problems
>
>
> > This AVR newbie is using a tiny2313 and studio 4.11.
> >
> > I have timer1 configured for CTC with OCR1A.   OCIE1A is set in TIMSK.
> > Global interrupts are enabled.  Stepping thru the code in the simulator
> > shows OCF1A being set for 1 cycle but my interrupt vector is not being
> > jumped to.   My code is not clearing OCF1A and the datasheet says that
> > OCF1A will not be cleared until execution of the interrup vector.  Any
> > thoughts on what I am doing wrong?  Code below.
> >
> > Thanks,
> > Aaron
> >
> > ; configure Timer/Counter1
> >     ldi temp1,  0b00000000
> >                 ; 00------  ; Compare Output Mode for Channel A, Normal
> > Port Operation, OC1A & OC1B disconnected
> >                 ; --00----  ; Compare Output Mode for Channel B, Normal
> > Port Operation, OC1A & OC1B disconnected
> >                 ; ----00--  ; reserved
> >                 ; ------00  ; 00 = clear timer on compare match with
OCR1A
> >     out TCCR1A, temp1
> >
> >     ldi temp1,  0b00001001
> >                 ; 0-------  ; 0 = input capture noise canceler disabled
> >                 ; -0------  ; 0 = trigger capture on falling edge of IC1
> >                 ; --0-----  ; reserved
> >                 ; ---01---  ; 01 = clear timer on compare match with
OCR1A
> >                 ; -----001  ; 001 = no prescaler, internal clock
> >                 ; -----011  ; 011 = 1:64 prescaler, internal clock
> >     out TCCR1B, temp1
> >
> >     ldi temp1,  0b00000000
> >                 ; 0-------  ; 1 = force output compare for channel A
> >                 ; -0------  ; 1 = force output compare for channel B
> >                 ; --000000  ; reserved
> >     out TCCR1C, temp1
> >
> >     cli                     ; clear interrupts for 16-bit register
access
> >
> >     ldi temp1, 0x1F         ; 8Mhz clock -> 125 ns instruction cycle
> >     ldi temp2, 0x40         ; ...for a 1 ms delay we need 8000
> > instruction cycles
> >     out OCR1AH, temp1       ; ...8000 decimal = 0x1F40
> >     out OCR1AL, temp2
> >
> >     sei                     ; enable interrupts after 16-bit register
> access
> >
> >     ldi temp1,  0b01000000
> >                 ; 0-------  ; 0 = Timer/Counter1 Overflow Interrupt
> Disabled
> >                 ; -1------  ; 1 = Timer/Counter1 Output Compare A Match
> > Interrupt Enabled
> >                 ; --0-----  ; 0 = Timer/Counter1 Output Compare B Match
> > Interrupt Disabled
> >                 ; ---0----  ; reserved
> >                 ; ----0---  ; 0 = Timer/Counter1 Input Capture Interrupt
> > Disabled
> >                 ; -----0--  ; 0 = Timer/Counter0 Output Compare B Match
> > Interrupt Disabled
> >                 ; ------0-  ; 0 = Timer/Counter0 Overflow Interrupt
> Disabled
> >                 ; -------0  ; 0 = Timer/Counter0 Output Compare A Match
> > Interrupt Disabled
> >
> >     out TIMSK, temp1
> >
> > Loop:
> >    nop
> >    nop
> >    nop
> >    nop
> >    nop
> >    rjmp Loop
> >
> >
> >
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