Datasheet

MCP23017/MCP23S17
DS20001952C-page 12  2005-2016 Microchip Technology Inc.
3.0 DEVICE OVERVIEW
The MCP23017/MCP23S17 (MCP23X17) device
family provides 16-bit, general purpose parallel I/O
expansion for I
2
C bus or SPI applications. The two
devices differ only in the serial interface:
• MCP23017 – I
2
C interface
• MCP23S17 – SPI interface
The MCP23X17 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 (IODIRA/B).
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 16-bit I/O port functionally consists of two 8-bit
ports (PORTA and PORTB). The MCP23X17 can be
configured to operate in the 8-bit or 16-bit modes via
IOCON.BANK.
There are two interrupt pins, INTA and INTB, that can
be associated with their respective ports, or can be
logically OR’ed together so that both pins will activate if
either port causes an interrupt.
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.
2. 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.
3.1 Power-on Reset (POR)
The on-chip POR circuit holds the device in reset until
V
DD
has reached a high enough voltage to deactivate
the POR circuit (i.e., release the device from reset).
The maximum V
DD
rise time is specified in Section 1.0
“Electrical Characteristics”.
When the device exits the POR condition (releases
reset), device operating parameters (i.e., voltage,
temperature, serial bus frequency, etc.) must be met to
ensure proper operation.
3.2 Serial Interface
This block handles the functionality of the I
2
C
(MCP23017) or SPI (MCP23S17) interface protocol.
The MCP23X17 contains 22 individual registers (11
register pairs) that can be addressed through the Serial
Interface block, as shown in Table 3-1.
TABLE 3-1: REGISTER ADDRESSES
Address
IOCON.BANK = 1
Address
IOCON.BANK = 0
Access to:
00h 00h IODIRA
10h 01h IODIRB
01h 02h IPOLA
11h 03h IPOLB
02h 04h GPINTENA
12h 05h GPINTENB
03h 06h DEFVALA
13h 07h DEFVALB
04h 08h INTCONA
14h 09h INTCONB
05h 0Ah IOCON
15h 0Bh IOCON
06h 0Ch GPPUA
16h 0Dh GPPUB
07h 0Eh INTFA
17h 0Fh INTFB
08h 10h INTCAPA
18h 11h INTCAPB
09h 12h GPIOA
19h 13h GPIOB
0Ah 14h OLATA
1Ah 15h OLATB