MCP23009 Microchip Technology Inc., MCP23009 Datasheet - Page 16

• Manufacturer Part Number: MCP23009
• Description: 8-bit I/o Expander With Open-drain Outputs
• Manufacturer: Microchip Technology Inc.

MCP23009/MCP23S09
1.6.1
Controls the direction of the data I/O.
When a bit is set, the corresponding pin becomes an
input. When a bit is clear, the corresponding pin
becomes an output.
REGISTER 1-2:
DS22121A-page 16
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7-0
R/W-1
IO7
I/O DIRECTION REGISTER
IO7:IO0: Controls the direction of data I/O <7:0>
1 = Pin is configured as an input.
0 = Pin is configured as an output.
R/W-1
IO6
IODIR – I/O DIRECTION REGISTER
W = Writable bit
‘1’ = Bit is set
R/W-1
IO5
R/W-1
IO4
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
R/W-1
IO3
R/W-1
IO2
© 2008 Microchip Technology Inc.
x = Bit is unknown
R/W-1
IO1
R/W-1
IO0
bit 0