Introduction

　　The MAX3108 is a high-performance universal asynchronous receiver-transmitter （UART） in a wafer-level package （WLP）， ideal for low-power portable devices. Its advanced features range from individual 128-word transmit and receive FIFOs to extensive hardware-mediated flow control. However， before an application can take advantage of these features， it must reliably communicate with the MAX3108 and its 31 internal registers. This application note covers the basics of MAX3108 communication. Software conventions regarding the pseudocode appear in the Appendix.

　　Hardware Connectivity

　　Communication between the MAX3108 and the microprocessor （μP） occurs through 2， 4， or 6 pins. Two dedicated pins， IRQ and RST， typically connect to microprocessor GPIO pins. IRQ is an input pin to the microprocessor. As a dual-function signal， IRQ both indicates when a MAX3108 reset has been finished and notifies the microprocessor when certain programmable UART events of note have occurred. RST is an output pin from the microprocessor. It reliably forces a reset of the MAX3108 into a known state. Though it is possible to implement a functional application without using these pins， it is preferable to connect them unless there is a lack of GPIO pins.