what is the propagation delay through ppi

[Raj]

Hi all, in my project I have a input pin and out pin whenever pulse is raised on input pin I need to set out pin exactly after 8.3ms.

For these I'm using ppi by configuring input pin response to ppi channel1 event and timer1 start to ppi channel1 task and I set timer1 CC[0] a value corresponding to 8.3ms . And I take another ppi channel, timer1 CC[0] compare evt is added to ppi channel2 evt and out pin set task added to ppi channel2 task.

but I didn't get delay exactly 8.3ms due to propagation delay of ppi channel1 and channle2

So now I need to set the delay for 8.3ms-(propagation delay of ppi channel1+channel2)

I studied nRF51 data sheet and reference manual but I didn't find the prorogation delay for ppi task response, can any one tell me the prorogation delay for ppi task responce and I'm not using any power saving.

Thanks in advance

[Ole Bauck]

If you take the ppi delay alone it is about 1 clock cycle which equals 62.5ns. You can actually test this by using the code here and compare the pulse when using ppi to clear the timer instead of shorts.

If the peripheral you are using require some resources that are not on you will have to start these first. As the product specification says (part 3.4.2.2 System ON mode):

(…) The PPI task response will vary depending on the resources required by the peripheral where the task originated. The resources that could be involved are:

• 1V7 with the startup time t1V7
• 1V2 with the startup time t1V2
• One of the following clock sources

• RC16 with the startup time tSTART,RC16
• XO16M/XO32M with the startup time the clock management system tXO

but since you say that you don’t go into low power mode (__WFE() or sd_app_evt_wait) you should not need to worry about this.

Since you are using pin in and out event, the impedance on the pin may also affect the response. Typical pin capacitance is 4pF and typical pull-up resistance is 13KOhm. This circuit will have a rise and fall time.

What is the actual time you are measuring and how are you measuring it?