10uS Timer

[wayne millard]

Hi to all

How can i make a timer interrupt run at a 10us rate so that i can generate times to the nearest 10us.

Thanks,
Wayne

[medelec35]

Hiya Wayne
10uS = 1/ 10x10-6 =100KHz
So depending on osc speed, you can use timer 0 or If not using PWM, timer 2 to generate interrupt at that speed (time)
You have a choice of selecting a slightly shorter int time then using format:
count = count + 1
count < a_number
then count = 0: Flag = 1 etc
Or you select a slower int frequency and add tmr0l += a_number; (or tmr0 depending on your target device).

If you want to post a flowchart that is set up for your target chip and osc speed + type of osc.
Then I will see if I can add the 10uS int macro.
10us is very quick, wont leave much time for anything else

[wayne millard]

Thanks medelec35,

I have not started the project yet just need to get the timer working first then start on the project.
any help would be very grateful.

Wayne

[medelec35]

If you let me know target device, osc type. internal external etc and speed. I will create one for you to work with.

[wayne millard]

medelec35,

I will use a 18F4520 and some thing like a 10Mhz clock.

Thanks
wayne

[medelec35]

Here is a version with a 10uS interrupt
Note the higher the osc frequency the better.
So I have enabled osc PLL x 4
Now with a 10MHz osc, the chip will be running a 10x4 = 40MHz

[Harry Tuttle]

Hi medelec35,

I have not seen ! used before (Output = !Output), can you explain it's function?

Thanks,
ben

[medelec35]

(Output = !Output), can you explain it's function?

Thanks,
ben

Hiya Ben

I have used '=!' as a bitwise 'not equal to'.
So what it does is toggles the value of Output.
So If Output = 0 then after Output = !Output
Output will change to 1

If Output = 1 then after Output = !Output
Output will change to 0
etc.

So in this case was toggling port A0 every time interrupt was accessed.

I find it an easier method to learn than
Toggle = (Toggle XOR 0b11111111) AND 1

The 1 on the far right is the bit you want to toggle.
So if you want to toggle bit 3 you will need to use
Toggle = (Toggle XOR 0b11111111) AND 4
etc.