topic Re: LPSPI burst interface in S32K

LPSPI burst interface

joohau — Thu, 16 Jun 2022 07:39:23 GMT

We are investigating to use the burst interface of the LPSPI module of the S32K3xx MCU.

Is there any information or any example projects available that use this burst interface (TCBR, TDBR[0..127], RDBR[0..127] registers). The reference manual only writes that they are an alias of the normal registers (TCR, TDR and RDR) but there seems to be no information on how they can/should be used.

Some more specific questions:

What defines the moment at which an element from the TDBR register is pushed to the TDR FIFO
Does the LPSPI module keep an internal pointer to the current active element in the TDBR/RDBR register?
Can we reuse the content of the TDBR register after a burst has finished (to send the same burst of TX SPI commands again)?

Re: LPSPI burst interface

lukaszadrapa — Thu, 23 Jun 2022 09:14:29 GMT

Hi Joost,

I had to ask for the details because it's really missing in the reference manual. I'm afraid it will take more time. I will let you know later. Thanks for patience.

Regards,

Lukas

Re: LPSPI burst interface

R20220311 — Fri, 24 Jun 2022 07:12:01 GMT

@lukaszadrapado you have an update on this?
I'm also investigating the use of the TDBR register.

Re: LPSPI burst interface

lukaszadrapa — Fri, 24 Jun 2022 08:31:39 GMT

Hi Rob,

not yet. It was forwarded to design team and I'm afraid it will take a couple of days.

Regards,

Lukas

Re: LPSPI burst interface

lukaszadrapa — Fri, 01 Jul 2022 08:14:29 GMT

Hi Joost,

here is the feedback I just got:

"The TDBR is an alias, writing to any of those addresses is identical to writing to the TDR. There is no TDBR pointer or memory.

There are 2 main uses for this register:

Perform burst write into the TDR using the DMA. The benefit of this depends on the DMA controller and system bus connections (eg: the bus structure is such that a single 16-byte burst is more efficient than 4 single 32-bit transfers).
Use the DMA to write 32-bit to TCBR (setting up the command with respect to PCS, etc) and then increment into TDBR region for the data.

So you can use those registers as the normal ones."

Regards,

Lukas

Re: LPSPI burst interface

R20220311 — Mon, 04 Jul 2022 11:32:26 GMT

@lukaszadrapathanks for the answer.

Is it possible to ask for an Reference Manual update to include this explanation. Furthermore would it be possible to add a simple example in the reference manual explaining the use of these burst registers.

Re: LPSPI burst interface

lukaszadrapa — Mon, 11 Jul 2022 04:51:06 GMT

Sure, I will ask for that.