All the io lines are noise filtered with RC networks. The io lines that support analog inputs being the most heavily filtered( about 5x the normal digital io lines), the interrupt io pins being the least filtered (about .1x). Be aware that:
MYSPI_CLK = 1;
mask >>= 1;
MYSPI_CLK = 0;
would probably work ok in a bare PIC18F environment, but with the digital lines spec'd to max 50Khz response time (20us?) the above clock pulse will never show up at the IFI controller pin. You'd likely need to add lots of nop delay to wait for the rise time on the pin and also filter it through a schottky or some other type of buffer to clean up the slow rise "pulse" into a real clock edge.
http://www.ifirobotics.com/rc.shtml#Specifications
http://www.ifirobotics.com/docs/anal...al--i-o-rc.pdf