topic K8X SPI max speed (slave) in Kinetis Microcontrollers

K8X SPI max speed (slave)

felipeyamamoto — Wed, 15 Nov 2017 03:15:24 GMT

Hello,

SPI peripheral is clocked by bus clock (60 MHz), and is limited to bus clock/2 (30 MHz), according to the reference manual. However, the datasheet states that, when operating in slave mode, there is a limitation of 15 MHz to the module frequency. Why is that? Is this really the maximum speed that I can get from the SPI as slave? I need a transfer rate of ~30Mbps as a slave. Is there any serial interface available in the MCU that I can achieve this (using FlexIO, for example)?

Thanks in advance,

Re: K8X SPI max speed (slave)

jingpan — Thu, 16 Nov 2017 06:53:13 GMT

Hi,

15M is the maximum operating frequency is measured with non-continuous CS and SCK. When DSPI is configured with continuous CS and SCK, there is a constraint that SPI clock should not be greater than 1/6 of bus clock, for example, when bus clock is 60MHz, SPI clock should not be greater than 10MHz. This is because of the bit sampling in slave mode need more than 1 clock.
I'm not sure if flexio work as SPI can fast than 30M. Please refer to this post:

https://community.nxp.com/message/614738?et=watches.email.thread#614738

Regards

Jing