16.2 Digital I/O Configuration Register

The direction control register is programmed by writing to Base + 15 using the format below. Once you have set the port directions with this register, you can read and write to the ports as desired.

Digital I/O Configuration Register: Page 1, Base + 15

Bit No	7	6	5	4	3	2	1	0
Name	1	ModeC	ModeA	DirA	DirCH	ModeB	DirB	DirCL

Definitions:

1	Bit 7 must be set to 1 to indicate port mode set operation
DirA	Direction control for bits A7 – A0: 0 = output, 1 = input
DirB	Direction control for bits B7 – B0: 0 = output, 1 = input
DirCL	Direction control for bits C3 – C0: 0 = output, 1 = input
DirCH	Direction control for bits C7 – C4: 0 = output, 1 = input

ModeA, ModeB, ModeC I/O Mode for each port, 0 or 1

Here is a list of common configuration register values:

Configuration Byte

Hex	Decimal	PortA	PortB	PortC
9B	155	Input	Input	Input
92	146	Input	Input	Output
99	153	Input	Output	Input
90	144	Input	Output	Output
8B	139	Output	Input	Input
82	130	Output	Input	Output
89	137	Output	Output	Input
80	128	Output	Output	Output