I need to have another control register to control the new functions.  This register controls the hi-resolution mode, the keyboard access, the cartridge access, the bank switching of the RAM, etc.   I don't want it to get modified unintentionally, so I need it to be tied to the new instruction calls.  This is not too difficult, because I can use the /OVerride signal to drive it.  But I don't want all the /OVerride instructions to call it, so I chose to use one of the instructions ST AC->[0,D] and /OVerride to load the control register /LC.  Much like XOUT, the CTRL register loads from the AC register.  And at the same time, AC is stored to RAM at [0,D], so the programmer needs to be a little careful.

/LC = /OV or [0,D],AC 

likewise, /LC = /OV or (/IR2 and /IR3 and /IR4)