How to convert the DWT CYCCNT to ns ?

[gapryun]

Posted on July 15, 2014 at 17:26

Dear

I have read Ch16.2 Trace component DWT, the definition guide of Cortex M3 2nd. But I still confuse it. If I take the CYCCNT, the corresponding time is CYCCNT * 168 MHz * 1e9 ?Am I correct?  Thanks 

[Tesla DeLorean]

Posted on July 15, 2014 at 17:36

You understand the basic relationship between frequency and period, right?

At 168 MHz each tick is about 5.95ns[DEAD LINK /public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/How%20to%20convert%20the%20systick%20to%20ns&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&TopicsView=https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/AllItems.aspx&currentviews=5]https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fcortex_mx_stm32%2fHow%20to%20convert%20the%20systick%20to%20ns&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&TopicsView=https%3A%2F%2Fmy.st.com%2Fpublic%2FSTe2ecommunities%2Fmcu%2FLists%2Fcortex_mx_stm32%2FAllItems.aspx¤tviews=5

[gapryun]

Posted on July 15, 2014 at 17:49Sorry, clivel, My smartphone have strange problem so it did not submit my question.  For now, I have updated. And thank you for your nice reply.

[Tesla DeLorean]

Posted on July 15, 2014 at 17:58

This forum does not work well with smartphones or tablets

>> CYCCNT * 168 MHz * 1e9 You need to make an initial, and final measurement, and subtract them to understand how many ticks occurred in the measurement period. Then  (DeltaTicks / 168000000.0) * 1e9 would give you nanoseconds