4 - Basic peripherals

Abstract

This chapter describes the basic peripherals that most microcontrollers provide. It discusses parallel ports which are the simplest input/output (I/0) devices, timer counters for generating and measuring time- and count-based events, serial interfaces and direct memory access (DMA) controllers. Parallel ports provide the ability to input or output binary data with a single bit allocated to each pin within the port. They are called parallel ports because the initial chips that provided this support grouped several pins together to create a controllable data port similar to that used for data and address buses. It transfers multiple bits of information simultaneously, hence the name parallel port. Although the name implies that the pins are grouped together, the individual bits and pins within the port can usually be used independently of each other. These ports are used to provide parallel interfaces such as the Centronics printer interface and output signals to light emitting diodes (LEDs) and alphanumeric displays.