I have other devices on my SPI bus that I'd like to communicate with at 4MHz. The 7816 lives on the same SPI bus. When I talk to the 7816 I always set the SPI clock to 2MHz, but I'd like to set the SPI clock to 4MHz when I talk to the other devices.
Is it OK to "overclock" the 7816's SPI clock so long as /CS isn't asserted at the time? Does the 7816 ignore SCLK when /CS isn't asserted?