TIMER0 Interrupt on F28335

Enea Bianda

Hi,

I have an eZdspF28335 board and I need to sample a signal with a rate of 5 MHz in order to calculate his derivative. To perform this task I set TIMER0 to have an interrupt every 30 cycles (200 ns). The interrupt function sample the signal and do the necessary computations. The problem is that to enter in the interrupt function it takes about 20 cycles, so only 10 cycles remain to do the rest... Can someone help me?

Thank you

Enea

over 16 years ago

Tim Love over 16 years ago

TI__Expert 5340 points

Enea Bianda,

Unfortunately there is overhead to enter an interrupt. For internal interrupts the minimum latency is 14 cycles. This can grow due to wait states, INTM, etc. You can view a diagram of the latency at the following link:

http://community.ti.com/members/277171/files/28x_5F00_interrupt_5F00_latency.jpg.aspx

Regards,

Tim Love

Enea Bianda over 16 years ago in reply to Tim Love

Prodigy 50 points

Hi Tim, thank you for the answer. Could you suggest me a better way to do my task in order to not have a latency?

Regards,

Enea Bianda

Mr M over 16 years ago in reply to Enea Bianda

Prodigy 90 points

Do it without an interrupt. Just read the timer counter value in a loop.

Make the timer counter tick every 200ns (free running). So when the timer value changes you do your stuff.

[H]

Tim Love over 16 years ago in reply to Mr M

TI__Expert 5340 points

You may also have to test how much overhead you get with this method as well. Each C statement will produce a few lines of assembly code that will take cycles. You probably will not see any overhead like the interrupt but the downside is you are running a continuous loop of code that will draw power due constantly consuming the CPU. If power is not an issue then this may be the best solution.

Regards,

Tim Love

C2000™︎ microcontrollers

C2000 microcontrollers forum

TIMER0 Interrupt on F28335