IOCON for pins not configured as GPIO

[lpcware]

Content originally posted in LPCWare by Dill on Tue Sep 08 02:59:20 MST 2015
Hello,

when I configure a pin as GPIO I understand how to set the IOCON registers.

But what to do when I select another function? Do MODE, HYS, INV, OD and S_MODE have any effect then anyway? (in the pad configuration figure in the datasheet, eg fig 48 in the 11xx UM I'm not sure if these gates are only connected to the pin if GPIO function is selected.)
Should I leave everything as default, i.e. when I use lpcopen's Chip_IOCON_PinMuxSet set the modefunc param to the reset values?

What happens when I write to the reserved bits. (for example IOCON_DIGMODE_EN to a standard digital pin)

Thanks!

[lpcware]

Content originally posted in LPCWare by Dill on Thu Oct 01 05:59:24 MST 2015
It looks like for XTALIN and XTALOUT it is not correct to keep the reset values, the pulls need to be disabled...!?

[lpcware]

Content originally posted in LPCWare by mc on Thu Sep 17 09:49:00 MST 2015
Hi Dill,
Yes, In case of functions other than GPIO, normally you will use default values of MODE, HYS, INV, OD and S_MODE. However  some time, you can change value according to your requirements. For example in LPC11U6x_E6X you can change I2c modes(bit9:8). Please check
I2C open-drain pin control registers (PIO0_[4:5], addresses 0x4004 4010 (PIO0_4) to 0x4004 4014 (PIO0_5)) bit description

in the UM of this device.