Looking at the reference manual for the MPC5554, it appears that the SIU only provides the ability to write to one bit at a time using the SIU_GDPOn registers. This is a problem for me, as I need to write out to multiple pins in one atomic operation. I need to be able to write to at least 8 GPIO pins in one operation, actually, in order to interface with external hardware which is not synchronized with the clock of the chip. Is this possible? Is there another interface that allows writes to multiple output lines at once? I'm not seeing it in the reference manual but maybe I'm looking in the wrong place.