A8-A15		$FE00		IOSEL
A4-A7
	7654
	0010	$FE20		
	0011	$FE30


BUS		WDC65C22x2	74HC138			Notes
-------------------------------------------------------------
A0		RS0
A1		RS1
A2		RS2
A3		RS3
A4				A			SEL
A5				G1			HIGH	
A6				B			LOW
A7				C			LOW
IOSEL				G2A/G2B			LOW
		CS2-1		Y0			$FE20
		CS2-2		Y1			$FE30
+5		CS1-1
+5		CS1-2

================================================================

Headers
----------
GND	+5
P0	P1
P2	P3
P4	P5
P6	P7
C1	C2
+5	GND