This document describes the basic issues that need to be addressed in order to implement digital signal processing systems using the PIC16C74 and provides application code modules and examples for DTMF tone generation, a 60 Hz notch filter, and a simple PID compensator for control systems. These routines can also be used with other PIC16C6X and PIC16C7XXX processors with minor modifications and the addition of external analog I/O devices.
The note introduces the use of the PIC16C74 microcontroller for low‑end digital signal processing, describing its on‑chip A/D converter, PWM module, and fast instruction speed. It outlines a typical DSP system architecture, including A/D conversion, processing, and D/A reconstruction.
Detailed sections cover development tools, number representation, A/D/D/A interfacing, tone generation, digital filter implementation, and PID control. Example programs demonstrate DTMF tone generation, a 60 Hz notch filter, and a PID compensator, with performance results and implementation notes.
| A/D converter resolution | 8‑bit |
|---|---|
| PWM resolution | 8‑bit |
| Instruction execution speed | as fast as 200 ns per instruction |
| Single‑tone generation cycles | ~125 instruction cycles per output sample |
| Sample rate used in DTMF example | 6.5 kHz |
The document focuses on the PIC16C74 microcontroller.
It needs approximately 125 instruction cycles per output sample for a single tone.
The PWM module has an 8‑bit resolution.