SPI master mode 36 mbps - is this possible?

[sonycman]

Posted on June 01, 2009 at 11:04

SPI master mode 36 mbps - is this possible?

[sonycman]

Posted on May 17, 2011 at 13:13

Hello!

I've got STM32F103RBT6 and its reference manual says that maximum SPI clock might be 18 MHz only. This is very strange, because SPI1 module can be clocked through AHB with frequencies up to 72 MHz thus having module working at 36 MHz. What do you think, guys? Anybody tries that already? [ This message was edited by: sonycman on 27-05-2009 14:02 ]

[alex_ribe]

Posted on May 17, 2011 at 13:13

Hi:

The limitation may come from the internal design of the SPI module, as it might require 2 or 4 peripheral clock cycles to read the data correctly. 18MHz it still good, as other SPI modules in other MCUs have even lower communication speeds (specially in Slave mode). Regards, Alex.

[sonycman]

Posted on May 17, 2011 at 13:13

Quote:

On 27-05-2009 at 16:39, Anonymous wrote: The limitation may come from the internal design of the SPI module, as it might require 2 or 4 peripheral clock cycles to read the data correctly. 18MHz it still good, as other SPI modules in other MCUs have even lower communication speeds (specially in Slave mode). Thank you, Alex. But slave mode is not the case for me. Usually, master mode SPI clock is equal to peripheral clock divided by 2. This is just what we have in STM32. Thus I see no problem running SPI1 at 36 MHz (72/2) theoretically. But, before making changes in physical circuit, I need some practical proof this is really works. Chip`s developers or experienced users must know the answer. I`am really will be very grateful for any help from them 🙂 Vladimir.[ This message was edited by: sonycman on 27-05-2009 22:17 ]

[stevemelnikoff9]

Posted on May 17, 2011 at 13:13

Although it is theoretically possible for the SPI to be clocked faster, as you noted, the reference manual states a maximum value.

It's likely that this is fast as they can guarantee that the SPI module will work. You can try a higher speed, but don't be surprised if it doesn't function correctly! Steve.

[st3]

Posted on May 17, 2011 at 13:13

Quote:

Chip`s developers ... must know the answer.

I imagine that the answer from the chip's developers is what is written in the User Manual?! 8-)