TMS320F28388D: TMS320F2838x: reading SPIRXBUF with Lauterbach script does decrement RXFFST

Hi all,

I am using the SPI in MasterMode, closed in loopback, 16 bits width, Tx and Rx FIFOs enabled.
When the application writes N words (with N < 16) into the tx FIFO (SPI_writeDataBlockingFIFO) and then, as soon as RXFFST is N, reads N times (SPI_readDataBlockingFIFO) from rx fifo (SPIRXBUF register), the data are correctly read in the same order as they were written, and every time a word is read from SPIRXBUF register, the RXFFST counter in SPIFFRX is also decremented as expected.

So, everything is fine, as described in the User Manual: "If FIFO mode is enabled, reading this register will also decrement the RXFFST counter in SPIFFRX."

But if I try to do the same with a Lauterbach script, this does not work. RXFFST counter reaches correctly N, but every later read from from SPIRXBUF register does not decrement the RXFFST counter, therefore only the first word is continuously read from SPIRXBUF. Reading SPIRXEMU has the same effect.

Please note that with Lauterbach, I also tried to configure the SPI in "Emulation Free Run" (FREE bit of SPIPRI register), but this does not help.

Any idea?

over 5 years ago

0 Manoj Santha Mohan over 5 years ago

TI__Guru 55700 points

DB,

Emulation read of SPIRXBUF register will not change the RXFFST counter contents. Only CPU reads of SPIRXBUF register content affect RXFFST counter.

I'm wondering whether your script is doing a emulation read using Lauterbach script.

Regards,

Manoj

0 DB over 5 years ago in reply to Manoj Santha Mohan

Prodigy 20 points

Thanks for reply.

How to have a proper FIFO usage with a Lauterbach script?

The only way I could find is to reset the both FIFOs after each word transmit/receive, but it is like to have a 1-word long FIFO, which makes the script much slower.

0 Manoj Santha Mohan over 5 years ago in reply to DB

TI__Guru 55700 points

I have never used Lauterbach script. So, I really can't comment on that.

Essentially you need to do CPU read of SPIRXBUF register in a loop to read the contents stored in SPI RX FIFO.

Regards,

Manoj

+1 DB over 5 years ago in reply to Manoj Santha Mohan

Prodigy 20 points

Thanks for reply. In that case, I can just use only one FIFO element from Lauterbach script and then reset the FIFO.

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TMS320F28388D: TMS320F2838x: reading SPIRXBUF with Lauterbach script does decrement RXFFST