33 NCO - Numerically Controlled Oscillator Module

The Numerically Controlled Oscillator (NCO) module is a timer that uses overflow from the addition of an increment value to divide the input frequency. The advantage of the addition method over a simple counter driven timer is that the output frequency resolution does not vary with the divider value. The NCO is most useful for applications that require frequency accuracy and fine resolution at a fixed duty cycle.

Features of the NCO include:
  • 20-Bit Increment Function
  • Fixed Duty Cycle (FDC) mode
  • Pulse Frequency (PF) mode
  • Output Pulse-Width Control
  • Multiple Clock Input Sources
  • Output Polarity Control
  • Interrupt Capability

The following figure is a simplified block diagram of the NCO module.

Figure 33-1. Numerically Controlled Oscillator Module Simplified Block Diagram