26 NCO - Numerically Controlled Oscillator

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 simple counter driven timer is that the output frequency resolution does not vary with the divider value. The NCO is most useful for application that requires 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

Figure 26-1 is a simplified block diagram of the NCO module.

Figure 26-1. Numerically Controlled Oscillator Module Simplified Block Diagram