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PDF AN1043 Data sheet ( Hoja de datos )
| Número de pieza | AN1043 | |
| Descripción | Unique Features of the MCP23X08/17 GPIO Expanders | |
| Fabricantes | Microchip | |
| Logotipo |  |
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AN1043
Unique Features of the MCP23X08/17 GPIO Expanders
Author: Pat Richards
Microchip Technology Inc.
INTRODUCTION
GPIO expanders provide easy I/O expansion using
standard serial interfaces. GPIO products are used to
increase the I/O on an MCU or provide remote I/O
using a serial interface.
This application note discusses the feature set and use
of the MCP23X08/17 (8-bit and 16-bit) GPIO Expand-
ers.
The MCP23X08 are 8-bit GPIO Expanders:
• MCP23008: I2C™ Interface
• MCP23S08: SPI Interface
The MCP23X17 are 16-bit GPIO Expanders:
• MCP23017: I2C Interface
• MCP23S17: SPI Interface
The functions and features of the MCP23X08 and
MCP23X17 are basically the same, except where
otherwise noted.
FEATURES
This application note discusses some of the features of
the MCP23X08/17 and how they may be used in an
application:
• I/O Port Description
• 8/16-Bit Mode (MCP23X17 only)
• Interrupt Features
- Mapping Interrupts
- Mirroring Interrupts (MCP23X17 only)
- Servicing Interrupts
• Internal Address Pointer Control
• Hardware Address Pin on SPI
I/O PORT DESCRIPTION
The I/O port is highly configurable for maximum
flexibility. Figure 1 is a simplified block diagram of an
I/O port pin. The port can either drive logic levels on the
pin, or read logic levels from the pad. The level on the
pad can be read at any time, regardless if the pin is
configured as an input or an output.
The IODIR register controls the direction of the pins
(input or output). More specifically, the IODIR registers
simply enables/disables the output driver. When the
driver is activated (IODIR = 0), the pad is driven to the
state in the latch register (OLAT). When deactivated
(IODIR = 1), the driver is high impedance.
The I/O port has multiple, individual configurations.
Each pin can …
• …be configured as an input. The output driver is
disabled (high impedance)
• …be configured as an output. The output driver
is enabled and the value in the latch is driven on
the pin.
• …enable a weak pull-up resistor
• …emulate an open-drain configuration. This is
accomplished by clearing the output latch (OLAT)
bit to a zero and using the direction register
(IODIR) to set the level on the pin. A pull-up
resistor is required to pull the pin to voltage when
the pin is an input
- To drive a 0: configure the pin as an output
(IODIR = 0) so the port drives whatever is in
OLAT (logic 0 in this case)
- To float a 1: set the pin as an input
(IODIR = 1). The output driver is disabled
and the pull-up resistor pulls the pin to a
logic 1
© 2006 Microchip Technology Inc.
DS01043A-page 1
Free Datasheet http://www.datasheet4u.com/
1 page  
AN1043
INTERNAL ADDRESS POINTER
CONTROL
Some slave serial devices automatically increment
their internal address pointer after each byte is clocked
by the master. This allows the master to sequentially
access multiple registers without re-sending the write
or read command.
Other slave devices do not automatically increment
their internal address pointer.
The MCP23X08/17 family of devices have the ability to
do either by configuring a control bit (IOCON.SEQOP).
This allows maximum flexibility when accessing the
registers.
For example, when configuring the device, it may be
desirable to allow the address pointer to automatically
increment so the device does not have to be re-
addressed after every byte.
Likewise, when performing a continuous operation on
a register (e.g., changing the outputs on a regular basis
by writing to GPIO or OLAT), it may be beneficial to
disable the address incrementing feature so that the
register is always accessed without re-addressing the
register.
FIGURE 5:
8-BIT MODE: ADDRESS POINTER DISABLED (MCP23008 EXAMPLE)
When the address pointer is DISABLED and the device is in
8-bit mode, the address pointer will not increment the
address pointer.
S 0100aaa0A 00001010A 10101010A 01010101A 10101010P
MCP23X08
Opcode
Register
Addr = 09h
Data @
09h
Data @
09h
Data @
09h
GPIOA
OLATA
IODIRB
IPOLB
GPINTENB
DEFVALB
INTCONB
IOCON
GPPUB
INTFB
INTCAPB
GPIOB
OLATB
09
0A
10
11
12
13
14
15
16
17
18
19
1A
See Figure 5 and Figure 6 for address pointer examples for the
MCP23X08 8-bit devices and Figure 7 and Figure 8 for the
MCP23X17 examples.
© 2006 Microchip Technology Inc.
DS01043A-page 5
Free Datasheet http://www.datasheet4u.com/
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet AN1043.PDF ] | |
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