Hi experts,
    I got a FTDI device module UMFT4222EV-D, my target are using a GPIO pin and a channel SPI with clock running as 40M Hz.
    So, I looked up the data sheet of the module UMFT4222EV and chipset FT4222, and found it supports different maximum clock frequency.

    In the "UMFT4222EV - USB2.0 to QuadSPI/I2C Bridge Development Module Datasheet Version 1.4" from the FTDI website.
   

3 FT4222H Features and Enhancement
...
The max SPI interface operating clock can be set up to 30MHz in master mode and 20MHz in slave mode.
...

    In the "FT4222H USB2.0 TO QUADSPI/I2C BRIDGE IC Datasheet Version 1.5" from the FTDI website.
   

4.1 Key Features
...
The maximum SPI interface operating clock can be set up to 40MHz in master mode and 20MHz in slave mode.
...

    There is 10MHz lost on UMFT4222EV-D device in master mode, what's going on the device? and for my target, which device I can use? Is there a suggestion?
   
Thanks
TonySH