How to check timer flag without enabling interrupt?

[mayur.k.vadukul]

Hi,

I am writing a code whereby I am using timer1 without interrupt. i.e. I am loading a value in the Timer1 but not enabling interrupt.

How can I check whether my Timer1 flag in CCS compiler whether it has overflown or not?
_________________
MVadukul

[temtronic]

You can just read whatever register the flag is in, mask off the other bits (or 'bit test' )

[Ttelmah]

The timer flag sets even if the interrupt is not enabled.

[mayur.k.vadukul]

I am writing as follows:-

setup_timer_1(T1_DISABLED);
setup_timer_1 (T1_INTERNAL|T1_DIV_BY_8);
set_timer1(DELAY_300USEC);

DELAY_300USEC = 0xff95
System Clock is 4MHz
Cycles required = 0.0003/0.00000025 = 1200
To make 1200 we can have division by 8 and 16 bit counter of 150 so we will load 65535-150 = 65385.

But for some reason when I am doing following after above it is not entering the loop below:-

if (interrupt_active(INT_TIMER1))
{
setup_timer_1(T1_DISABLED);
clear_interrupt(INT_TIMER1);
output_bit (CLK2, temp_flag_bit);
temp_flag_bit = ~temp_flag_bit;
setup_timer_1 (T1_INTERNAL|T1_DIV_BY_8);
set_timer1(DELAY_300USEC);
}

When I debug, it reaches the if loop but doesn't go in. i.e. my timer does not seem to be running.
_________________
MVadukul

[temtronic]

if I'm reading your code right,

the first thing you do is disable the timer....

so if don't enable the timer you'll never get the 'flag' set.

[mayur.k.vadukul]

I have picked this code form the CCS help file.

When I check I understood as when I disable it, it should stop as you said.

However, when the next line of code executes, it should enable the timer. should it not?

setup_timer_1(T1_DISABLED);
setup_timer_1 (T1_INTERNAL|T1_DIV_BY_8);
set_timer1(DELAY_300USEC);
_________________
MVadukul

[temtronic]

I would say no.


There's a specific option to disable the timer
setup_timer_1(T1_DISABLED);
this command 'stops' the timer from operating

setup_timer_1 (T1_INTERNAL|T1_DIV_BY_8);
this command says to connect Timer one internally to a clock source AND divide the rate by a factor of 8.

It does not specifically say 'enable' the timer

You should post which PIC though, as options for timers have changed over the decades. Some timers can have 'gates' to allow when the clock signal to actually be counted.

here's an example that I've cut/pasted the following from the PIC16F877C datasheet, Timer1 chapter...

TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1

.....
so in this old PIC, you CAN 'start/stop' the action of timer1 by set/clr the TMR1ON bit.

You can think of it this way.Your car has a standard transmission
You can say 'setup_timer_1 (T1_INTERNAL|T1_DIV_BY_8); ' runs the engine and puts transmission into 1st gear...

Nothing happens...you don't go anywhere

Now 'setup_timer_1(T1_enabled)' engages the clutch (connects engine to transmission ) and you drive down the road.

[mayur.k.vadukul]

Thanks for your help.

The issues are in the device's .h files whereby the constants they defined do not tie up with the datasheet's register. T1_INTERNAL should turn on the Timer and place it under the internal source as well. The value it has is 0x07. i.e. 0000 0111. But when I looked at the datasheet to select internal source, it should be 0000 0001 and the LSB is actually to turn ON the timer.

Once I define my own value as below, it started working how it should do.

#define TIMER1ON 0x81
setup_timer_1 (T1_DIV_BY_8|TIMER1ON);
set_timer1(DELAY_300USEC);

The issue is in 18F65J11.h file.

Many thanks for your comments.
_________________
MVadukul

[temtronic]

happy you got it working !!

email CCS about it, they can update that header in new compiler version.

[Ttelmah]

Yes. It actually wants to be 0x81 (the compiler assumes 16bit reads and
writes).

[leach67]