TMS320F28335: Precise delay

Frank Lee96

Part Number: TMS320F28335

Hi TI,

I'm using your TMS320F28335 MCU.I meet a problem that how should I do to produce a precise time delay under the circumstance where the timer isn't used?

Best regards,

Frank

over 7 years ago

0 Disona over 7 years ago

Genius 3050 points

Hello, Frank

How long delay do you want to achieve? How precise should it be?
There is a function "DELAY_US()" in TI examples - it can give you delay in microseconds.

You can also set your own function consisting of "nop" operations.

Why can't you use a timer for a delay though?

0 Frank Lee96 over 7 years ago in reply to Disona

Intellectual 830 points

precision:up to clock period.A ' nop' delay a clock period?

0 Disona over 7 years ago in reply to Frank Lee96

Genius 3050 points

Yes. One "nop" instruction takes one CPU cycle.

0 Frank Lee96 over 7 years ago in reply to Disona

Intellectual 830 points

On the other words,when the CPU runs at 120MHz,a 'NOP' instruction takes about 1/120M=8.3ns?

0 Disona over 7 years ago in reply to Frank Lee96

Genius 3050 points

If the CPU pipeline was not flushed before "nop" instruction - then yes, "nop" takes 1 cycle = 1/120 MHz.

0 Frank Lee96 over 7 years ago in reply to Disona

Intellectual 830 points

Hi Disona,
Thanks a lot.Do you have related resources about this topic?
Regards,
Frank

0 Disona over 7 years ago in reply to Frank Lee96

Genius 3050 points

Unfortunately, i don't have any additional information. I suggest you try to create a delay and measure it with a CPU timer to check, if it works correctly.

0 Ken Schachter over 7 years ago in reply to Disona

TI__Genius 17315 points

Frank,

See the following workshop:

processors.wiki.ti.com/.../C2000_Multi-Day_Workshop

In Lab 5 use the DelayUs.asm file and modify for your device. This one is for the F2837x devices, but I have it well commented so it should be easy to modify for the F28335. As Disona pointed out, this will be precise since it is based on the device clock.

I hope this helps. If this answers your question, please click the green "Verified Answer" button. Thanks.

- Ken

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28335: Precise delay