AN1043

AN1043 Unique Features of the MCP23X08/17 GPIO Expanders Author: Pat Richards Microchip Technology Inc. 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 … 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 Expanders. 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. …be configured as an input. The output driver is …be configured as an out...