MCP23S17 Expander: Features, Pinout, and Datasheet

For I²C bus or SPI applications, the MCP23S17 device family enables 16-bit general-purpose parallel I/O expansion. The MCP23017 is the same as the MCP23017. The serial interface is the only difference between the two devices:

• MCP23017 – I²C interface

• MCP23S17 – SPI interface

Multiple 8-bit configuration registers for input, output and polarity selection make up the MCP23X17. By writing the I/O configuration bits (IODIRA/B), the system master can activate the I/Os as either inputs or outputs.

The data for each input or output is stored in the input or output register that corresponds to it. The Polarity Inversion register inverts the polarity of the Input Port register. The system master has access to all registers.

The 16-bit I/O port is actually two 8-bit ports connected together (PORTA and PORTB). IOCON.BANK can be used to set the MCP23X17 to work in either 8-bit or 16-bit mode.

INTA and INTB are two interrupt pins that can be linked to their respective ports or logically ORed together to activate both pins if either port triggers an interrupt.

The interrupt output can be set to activate under two (mutually exclusive) conditions:

1. When the state of any input differs from the state of the Input Port register. This is used to notify the system master when a status has changed on an input.

2. When an input state differs from a register value that has been pre-configured (DEFVAL register).

The Interrupt Capture register saves the interrupt state by capturing port values at the moment of the interrupt.

The Power-on Reset (POR) resets the device state machine and resets the registers to their default values.

To determine the device address, the hardware address pins are employed.

Symbol

Footprint

3D Model

• 16-Bit Remote Bidirectional I/O Port:

- I/O pins default to input

• High-Speed I2C Interface (MCP23017):

- 100 kHz

- 400 kHz

- 1.7 MHz

• High-Speed SPI Interface (MCP23S17):

- 10 MHz (maximum)

• Three Hardware Address Pins to Allow Up to

Eight Devices On the Bus

• Configurable Interrupt Output Pins:

- Configurable as active-high, active-low or

open-drain

• INTA and INTB Can Be Configured to Operate

Independently or Together

• Configurable Interrupt Source:

- Interrupt-on-change from configured register

defaults or pin changes

• Polarity Inversion Register to Configure the

Polarity of the Input Port Data

• External Reset Input

• Low Standby Current: 1 µA (max.)

• Operating Voltage:

- 1.8V to 5.5V @ -40°C to +85°C

- 2.7V to 5.5V @ -40°C to +85°C

- 4.5V to 5.5V @ -40°C to +125°C

Microchip Technology MCP23S17-E/SO technical specifications, attributes, parameters and parts with similar specifications to Microchip Technology MCP23S17-E/SO.

Functional Block Diagram

Expanding I/O Ports of PIC Microcontroller using MCP23S1717 Expander

A microcontroller usually comes with a set of IO ports known as General Purpose Input Output (GPIO) ports. However, some applications require more IO ports than a microcontroller can provide. In these circumstances, IO Port Expanders can be used to expand a microcontroller's IO functionality. Microchip's MCP23017 and MCP23S17 are two such 16-bit IO expanders with Serial Interface. The MCP23017 employs a high-speed I2C interface, whereas the MCP23S17 employs a high-speed SPI interface.

Then, using the MCP23S17, we'll show how to extend the IO ports of a PIC Microcontroller. The built-in libraries in MikroC Pro for PIC Microcontroller allow you to communicate with the MCP23S17 via the SPI interface. Using the three address pins on the SPI Bus, we can link up to eight MCP23S17.

To demonstrate the operation of MCP23S17, we use the PIC 16F877A in this example project. MCP23S17's PORTA and PORTB are set to Input and Output, respectively. SPST switches and the MCP23S17's inbuilt PULL UP are connected to PORTA, while LEDs are attached to PORTB via current limiting resistors. Because the status of the SPST switches linked to PORTA is the status of the LEDs connected to PORTB, the LEDs connected to PORTB will GLOW according to the condition of the SPST switches connected to PORTA.

Circuit Diagram - I/O Port Expanding PIC Microcontroller

Notes: The PIC Microcontroller's VDD, VSS, and MCP23S17 are not depicted in the circuit design. VSS should be linked to OV and VDD should be connected to +5V.

When a switch is turned on, the associated LED is turned off, and when it is turned off, the corresponding LED is turned on. MCP23S17's address is 0 since all three address pins are grounded.

• Embedded Design & Development

• Automation & Process Control

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