AN1043 Datasheet | Microchip Technology

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)....