Maximum SPI Clock Speed

[VictorDiaconu]

Hi everybody, i need your help.

Our commpany are developing a new product on the base of LPC55s2x MCU. Now we are defining the pins routing. We need to implement a SPI Communication and LPC MCU is master also the communication speed ist very important for us.

I read the doku and now I'm not surre what is the maximum Clock Frequency for the FLEXCOMM0-7 of the LPC55s28.

In User manual (UM11126) at chapter 35.3 are wroted that : The Flexcomm Interface function clock frequency should not be above 30MHz master / slave 20MHz.

But in DataSheet Rev 1.8 (4March 2020) at chapter 7.23.3.2 are wrote that: Maximum supported bit rate for SPI master mode (transmit/receive) is 50 Mbit/s.

Now my questions what is realy maximum speed of SPI?

Thank you very mutch for your answers.

Best regards Victor

[VictorDiaconu · Accepted solution]

Thank You for your answer Omar.

Now it's clear for me. The Clock Frequency to Flexcomm0-7 must be maximum 48MHz, but after that for SPI in Master Mode at Physical layers it must be maximum 30MHz.

Best regards,

Victor

[Omar_Anguiano]

Hello

I will gladly clarify this. The speed of the SPI is measured in bit rate which is the amount of data transferred in a certain amount of time, for this device the bit rate in master is 50Mbits/s.

The User manual chapter 35.5 refers to the clock speed that feeds the flexcomm module. This clock is the one that allows us to reach the desired bit rate.

I see an issue since for the Flexcomm 7 to 0 the maximum clock is 48Mhz so the maximum bit rate is 48Mbit/s. The reason for this is on the chapter 35.7.4.1 and says that the SPI in master mode can run at the same or lower speed as the FCLK

Let me consult it with the corresponding team so I can give you the correct answer.

I will keep you updated, if you have more questions do not hesitate to ask me.

Best regards,

Omar

[Omar_Anguiano]

Hello

Thank you for waiting. Only the high-speed SPI (Flexcomm8) can reach 50Mbits/s. In the other flexcomm the maximum bit rate is 30Mbits/s.

Let me know if this is helpful, if you have more questions do not hesitate to ask me.

Best regards,

Omar