I'm working on the SC18IS600 chip (SPI to I2C converter) and have been having issues just communicating with it. At the moment I am attempting to configure the I2C Address register and set it to 0x3F or 0x00. When reading the address back however, I am getting (afaik) gibberish - it's not even reading back the default address value. While testing I noticed that the CS line goes low much earlier than the clock signal and want to know if the CS line must be synchronous with the clock when using SPI, or if a delay like the below image is acceptable. If anyone has other suggestions as to why this might not be working, please feel free to make them.
Edit for explanation: The 'gibberish' I was receiving was a result of not allowing for an 8us gap between each data word. The SC18IS600 requires this gap, further explained here for anyone else: https://community.nxp.com/thread/461576
datasheet at https://www.nxp.com/docs/en/data-sheet/SC18IS600.pdf