When does SPI Master STARTED event occur?

[maxv]

Hi,

There's no description at all in either the written text (31.3 SPI master transaction sequence) or the timing diagrams (Figure 71: SPI master transaction) showing precisely when the STARTED event occurs on the SPI Master. I'm referring to the nRF52832 PS 1.4.

How many clock cycles after the START task is triggered is the STARTED event emitted?

I'm trying to build a repetitive PPI-driven SPI master transaction, and am wondering if the CS pin can be driven low with proper setup + hold timing directly by using the STARTED event.

Thanks,
Max

[Simonr]

Hi Max

I don't think what you're describing is feasible, as there won't be enough time to do this by using the STARTED event. I'd rather suggest using a short timer to hold the timing instead, as there's only one cycle of the PPI (62.5ns I believe) from the START task until the STARTED event occurs.

Best regards,

Simon

[maxv]

Hi Simon,

Indeed, that is correct. 

I got the full SPIM transaction working using PPI by following the "Figure 71: SPI master transaction" diagram. CS needs to go active low before the START task anyways. So STARTED is not used at all in this case.

1 cycle between START and STARTED? Good to know.

Thanks,
Max