6 Mbps on SPI.

[Eric Provost]

Hello. I'm working with the nrf52 with s132 loaded. There is a way to have a 6Mbps on the SPI ? I try the value 0x60000000 but this do not work. Thanks. Eric Provost.

[Håkon Alseth]

Hi,

Anything over 4 MHz will be greatly influenced by pad and trace capacitance, so I would highly recommend checking the rise and fall time of your signal. You can generate a 5.3 MHz (16M / 3) signal by setting FREQUENCY = 0x48000000;, but not a 6 MHz frequency.

Cheers, Håkon

[Tim D]

@Håkon The FREQUENCY register is not defined that way in the datasheet. Can you provide more details of how you came up with 0x48000000 as the value to get a divide by 3? Is it possible to get a divide by 1 and run at 16MHz? What other values are possible in this register?

I am a little dumbfounded as to why the NRF51 has a 4MHz bus from a 16MHz main clock (div of 4) but the NRF52 has only a 8MHz bus from a 64MHz main clock (div of 8). 8MHz can be rather limiting, not to mention the 255 byte DMA cap and delay between clocks on the shortcut.