##### The idea is to use:
***
* X26 :  Q2 is doing changeover EMD
* X27 :  Q3 is doing changeover EMD

On Q1 DB1.X26 == DB1.DBX301.2
On Q1 DB1.X27 == DB1.DBX301.3
On Q1 DB1.X28 == DB1.DB301.4


So in this case using priority:
***
* Q1 can always change format because the AIR is taken from ALPLA
* Q2 can always start the change and will not pause.
	* When Q2 is changing is set the X26 bit
* Q3 must wait until X26 signal is off to start the changeover
	* If Q3 is doing the changeover and the X26 bit is set, then must pause until X26 is clear
	* When Q3 is changing is set the X27 bit
* Q4 must wait until X26 and X27 signal is off to start the changeover
	* If Q4 is doing the changeover and the X26 or X27 bit is set, then must pause until X26 and X27 are cleared.