S32K312 LPUART DMA transfers to the transmit FIFO

[li3]

Hi NXP，

    I am learning the LPUART of S32K312 and do not understand the description of 78.3.6DMA in the LPUART chapter of the chip manual. I have summarized the following questions, please kindly answer them in detail from NXP. Thank you.

1. Does this section indicate that LPUART uses DMA to send data?

2. Does this chapter indicate that DMA sends data to FIFO, and then FIFO sends data out?

3. Are the two areas mentioned in this chapter Transmit Command Burst (TCBR0-TCBR127) and Transmit Data Burst (TDBR0-TDBR255) DMA areas? Can you explain the functions of these two areas?

4, "two alias regions are implemented to support incrementing 8-bit, What does "16-bit,or 32-bit write accesses to the transmit FIFO" mean?

5. Can LPUART use DMA alone to transmit data? Does the code generated in RTD below use DMA alone?

Best regards,

Li 3.

[danielmartynek]

Hi @li3,

A1.

We can use DMA to send data either to the DATA register or to the allias registers in a burst, which can be more efficient than using single DMA transfers to the DATA register.

A2.

Yes

A3.

No, these are LUART registers, aliases to the DATA regiaster.

A4.

This is explained in the description of the registers RM rev.8:

77.6.1.23 Transmit Command Burst (TCBR0 - TCBR127)

77.6.1.24 Transmit Data Burst (TDBR0 - TDBR255)

A5.

The driver does not use the DMA burst, it uses DMA to transfer data to and from the DATA register.

Regards,

Daniel

[li3]

Hi Daniel，

    How much memory is the FIFO of each LPUART in S32K312 and how many characters can be stored?

    It is written in the chip manual that the FIFO memory of LPUART channel 0-1 is 16 characters, and the FIFO space of channel 2-7 is 4 characters, right?

    However, the FIFO space size of the S32K312 chip written in Chapter 78 of the chip manual is 4 characters, why? Which is accurate?

Best regards,

Li 3

[danielmartynek]

Hi Li 3,

The description in Section 77.6.1.3 Parameter (PARAM) is for S32K3xx in general.

Section 77.1 Chip-specific LPUART information is specific to S32K312 and other derivatives.

The information in Section 77.1 is correct.

Regards,

Daniel

[li3]

Hi Daniel，

    The FIFO space size of S32K312 in the following figure is 4 words does it mean that 16 characters can be stored?

    That means the maximum Watermark can be set to 16, right?

Best regards,

Li 3