Piccolo SPI SPISTE Question

David thanks for your advise. It gets better now. I have two questions more:

1. In spruh18d -F28069Technical manual, it reads

"8. FIFO status bits. Both transmit and receive FIFOs have status bits TXFFST or RXFFST (bits 12− 0)
that define the number of words available in the FIFOs at any time. The transmit FIFO reset bit
TXFIFO and receive reset bit RXFIFO will reset the FIFO pointers to zero when these bits are set to 1.
The FIFOs will resume operation from start once these bits are cleared to zero"

on page 849. And on page 861

"13 TXFIFO Reset          Transmit FIFO reset
                             0          Write 0 to reset the FIFO pointer to zero, and hold in reset.
                             1          Re-enable Transmit FIFO operation"

How should we approach?

2. How should I check, whether there is a byte received into buffer (yes, I've set the word length to 8bits)? 

This is what I am trying now:

 spi_xmit(0x0000); // Dummy command to read 8Bit
 // Wait until FIFO is empty
 while(SpiaRegs.SPIFFTX.bit.TXFFST >= 0) { }
 // Wait until data is received
 while(SpiaRegs.SPIFFRX.bit.RXFFST <1) { }
 rdata = SpiaRegs.SPIRXBUF;

However, I see more than 2 words -probably remnants of previous transmission data (RHS 8 bits?) which does not correspond to real alarm.

3. This one is extra :). In order to send >16bits within a single SPISTE pulse, I had to make SPIFFCT registers' FFTXDLY delay bits to zero. Otherwise, SPISTE pulses are generated for each word. 

Best Regards,
Adnan Kurt

Thanks David.

Concerning the second question: I need to use FIFO to transmit various length seamless data (8bit, 16 bits, and 32 bits) with uninterrupted SPISTE pulse. Sİnce I have to send 8 bit command to the e2prom, and i have to put Left Shifted 8 bit value to the buffer as advised in user's guide. So, remaining 8 bits are kept in FIFO (hope i have understood it correctly). Those built the garbage, I thought. Your advise to make note of "RXFFST prior to calling spi_xmit()" will be a better technique, thanks alot.

Regards,
Adnan

Thanks David. Sorry for taking your time, but if you would reconsider the waveform I have attached to the initial message, the scheme that you suggest would not work, right?  It seems, 8bit command embedded into a 16bit value would not work easily, the way you explain.

Regards,
Adnan

David, that's true. A write signal scheme is:

Before this sequence, an 8-bit WriteEnable command must be send and SPISTE must be driven high. So, that forced me to set SPI to 8-bit wide, and when writing, I send 4 off 16bit words, which were 8bit values left shifted. eg. 0x1234000, high byte corresponding to the commands, address values, etc. 

So, it works well. The only thing to take care of is those FIFO garbage.

Best,

Adnan

Hi David,

Can you please suggest how I can receive a 32 bit data as well? I am using the 28035 and would like to send and receive unbroken 32 bit data? Please let me know..

Kind regards,

Bartho

"In the master mode, SPISTE goes active 0.5tc(SPC) (minimum) before valid SPI clock edge. On the trailing end of the word, the SPISTE will go inactive 0.5tc(SPC) after the receiving edge (SPICLK) of the last data bit, except that SPISTE stays active between back-to-back transmit words in both FIFO and non-FIFO modes."

This is only valid on 28069, not on 28035 devices, right?
I did not find this annotation in the sprug71b 28035 SPI description - and I did not see this on my scope. Even when transmitting back-to-back, the SPISTE pin goes high in between the 4 16 bit words.

Stephan,

Please refrain from resurrecting old posts. If you have questions on an old post (especially 2 years old) create a new post, link to the original, and "mention" the person you are addressing your request to. This helps us track these posts much better.

To answer your question, the timings are noted in the Datasheet, not the User Guide chapter. If the SPISTE is toggling, I suspect that you are not truly transmitting the words back-to-back. are you using the FIFO or not? What are you using to determine when to transmit the next word?

-Mark