RM57L843: SCI TX with DMA operation: writing the 1st TX data by CPU is really needed?

Koichiro Tashiro

Part Number: RM57L843
Other Parts Discussed in Thread: HALCOGEN

Hi,

According to TRM section 29.4.2, the 1st TX data needs to be written by CPU even DMA is used.

Is this really required?
It seems HalCoGen example does not write the 1st data by CPU.
C:\ti\Hercules\HALCoGen\v04.07.01\examples\RM57Lx\example_sci_dma.c

Thanks and regards,
Koichiro Tashiro

over 4 years ago

+1 QJ Wang over 4 years ago

TI__Guru**** 199996 points

Hi Koichiro-san,

The DMA request is generated the moment TXRDY is set. When the SCI has completed transmission, the SCITXSHF register and SCITD are empty, the TXRDY bit is set, and an DMA request is generated, if DMA is enabled.

After SCI is initialized, the TXRDY should be set. I don't think you need to write the 1st data to SCITD register manually.

0 Koichiro Tashiro over 4 years ago in reply to QJ Wang

TI__Mastermind 22945 points

Hi QJ,

I see. I will submit request for TRM correction.

Thanks and regards,
Koichiro Tashiro

0 QJ Wang over 4 years ago in reply to Koichiro Tashiro

TI__Guru**** 199996 points

Thanks Koichiro-san

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RM57L843: SCI TX with DMA operation: writing the 1st TX data by CPU is really needed?