LPSPI burst interface

[joohau]

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)?

[lukaszadrapa]

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

[R20220311]

@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.

[lukaszadrapa]

Sure, I will ask for that.

[R20220311]

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

[lukaszadrapa]

Hi Rob,

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

Regards,

Lukas

[lukaszadrapa]

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