Microchip Technology GPIODM-KPLCD Data Sheet

DS21919E-page 5

MCP23008/MCP23S08

1.0

DEVICE OVERVIEW

The MCP23X08 device provides 8-bit, general
purpose, parallel I/O expansion for I

C bus or SPI

applications. The two devices differ in the number of
hardware address pins and the serial interface:
• MCP23008 – I

C interface; three address pins

• MCP23S08 – SPI interface; two address pins
The MCP23X08 consists of multiple 8-bit configuration
registers for input, output and polarity selection. The
system master can enable the I/Os as either inputs or
outputs by writing the I/O configuration bits. The data
for each input or output is kept in the corresponding
Input or Output register. The polarity of the Input Port
register can be inverted with the Polarity Inversion
register. All registers can be read by the system master.

The interrupt output can be configured to activate
under two conditions (mutually exclusive):
1.

When any input state differs from its
corresponding input port register state, this is
used to indicate to the system master that an
input state has changed.

When an input state differs from a preconfigured
register value (DEFVAL register).

The Interrupt Capture register captures port values at
the time of the interrupt, thereby saving the condition
that caused the interrupt.
The Power-on Reset (POR) sets the registers to their
default values and initializes the device state machine.
The hardware address pins are used to determine the
device address.

1.1

Pin Descriptions

TABLE 1-1:

PINOUT DESCRIPTION

Pin

Name

PDIP/

SOIC

QFN

SSOP

Pin

Type

Function

SCL/SCK

Serial clock input.

SDA/SI

I/O

Serial data I/O (MCP23008)/Serial data input (MCP23S08).

A2/SO

I/O

Hardware address input (MCP23008)/
Serial data output (MCP23S08).
A2 must be biased externally.

Hardware address input. Must be biased externally.

RESET

External reset input. Must be biased externally.

NC/CS

No connect (MCP23008)/External chip select input (MCP23S08).

INT

Interrupt output. Can be configured for active-high, active-low or
open-drain.

Ground.

GP0

I/O