ABSTRACT
This chapter focuses on digital communications techniques used in PIC interfacing with I/O devices, integrated circuits, and with other forms of programmable logic. It presents serial communications programming examples using the Universal Synchronous Asynchronous Receiver Transmitter module in the 16F877 PIC. The chapter provides circuits and sample code showing synchronous communications between a PIC and one or more shift register ICs. Digital and computer communications come in two flavors: serial and parallel. In the general literature, communications concerns often focus on transmission speeds, system performance, and minimum processing time. Serial communications take place by transmitting and receiving data in a stream of consecutive electrical pulses that represent data bits and control codes. In theory, synchronous communications implies that characters are sent out at a constant rate, in step with a clock signal. PIC communications can be designed both asynchronously and synchronously. Serial communications are often used in PIC programming, mostly due to the scarcity of available port lines.
