TMS320F28388D: How High is High Speed SPI?

Erhan,

Max SPI speed is 50 MHz at high speed mode and is supported only in high speed SPI pin mux options. I don't think other SPI pins will support 48 MHz baud rate.

To know max baud rate supported on non high speed mode pins, I need to confirm this with design team. It should take minimum of 2 weeks to get an answer.

Christmas holidays soon approaching, I realistically would expect answer from then in 1 week of Jan.

Regards,

Manoj

Hi Mohan!

Thank you for your help.

I think I can wait cuz I dont have other option. I need to learn max clk rate on non-high speed pin.

cheers,

Hi Manoj!

I would like to ask if is there any improvoment on this topic? We still want to know the maximum speed of the SPI in non-high speed mode.

cheers,

Hi Manoj!

Thanks for your answer. Then, here is my another question. I used SPI and CLB to read from 2 SPI slaves simultaneously. Thus, basically I used a counter inside of clb as shift register and connected clock of the spi to the shift register's clock. Then, I named shift register's input as MISO2. 

I think the limit of high speed spi is 40 MHz as far as I understood. So, if I use spi in high speed (12.5Mhz < SPICLK < 40Mhz) can CLB handle this speed also? I try to draw what i mean below in the picture.

Can I use CLB as spi at high speed as well? I checked that toggle frequency of any GPIO is 50MHz. Therefore, that looks possible. But can we confirm it?

Thanks in advance.

cheers,

Erhan,

I have forward your question CLB expert. Please provide a day (or) two for CLB expert to respond.

Regards,

Manoj

You are going to need to go through the SYNCHRONIZERs of the CLB so you will have some delay. You are trying to capture a 50MHz signal using the CLB?

Not 50MHz but it is limited to SPI CLK so 40MHz max right?

I didn't check the SYNCHRONIZER issue yet but my current configuration works now. As I said I want to read 2 SPI slaves simulataneously. Therefore I used SPI and a shift register from CLB. 

My question is when I use SPI high speed can CLB handle this speed and read data as well?

Eventually I want to read from 2 slaves(ads7883S) simultaneously at 24MHz or 36MHz or the best 48MHz(ads7883S limit).

cheers,

AS long as you use the HS GPIOs and then feed it into CLB and the max speed you are trying to use is operating correctly you should be fine.

You can run the CLB up to 150MHz using the pipeline mode if needed.

I have never read anything above 25MHz but as long as you assume 2-3 cycle delay from the synchronizers and everything still works you should be fine to proceed.

Hi Nima!

Thanks for the answer. I just checked that synchronizer for the CLB inputs were already enabled in my code.

I didn't know that there are high speed(HS) GPIO's in Delfino. What are  these HS GPIO's? Do you have a list of them? Do you know the limtis of them?

Or basically do you have a info about them?

cheers,

Can you check the datasheet? This device may support high speed spi on all pins I dont remember exactly.

Nima

Not all pins just some specific pins should be used for spi in high speed mode. What I mean is there is no GPIO called HS in TRM. 

With your logic I can assume that the GPIO's which are shared by peripherals like usb, ethernet, ethercat, fsi are high speed then. But we don't work with assumptions. :) Also then it brings another question that what is the limit speed of HS GPIO's?

Anyways, what I read is that GPIO max toggling frequeny is 50MHz and CLB can use any GPIO as input. If any GPIO can toggle at 50MHz then can it read 50MHz signal also? And then can I route this 50MHz to the CLB input's?

cheers,