How to configure for example pin PIO0_23 as input with MCLK function?
In IOCON register for this pin I can set function MCLK but there no option for direction.
Or I'm wrong and MCLK might just be only output.
I suppose that you use LPC55S69, if it is the case, pls refer to the section 4.5.6 in the UM11126.pdf. In other words, the MCLK control register controls the MCLK pin direction, in other words, the pin MCLK can be input or output, the MCLKIO determines the direction.
Hope it can help you