34 DSM - Data Signal Modulator Module

The Data Signal Modulator (DSM) is a peripheral that allows the user to mix a data stream, also known as a modulator signal, with a carrier signal to produce a modulated output. Both the carrier and the modulator signals are supplied to the DSM module either internally from the output of a peripheral or externally through an input pin. The modulated output signal is generated by performing a logical “AND” operation of both the carrier and modulator signals and then provided to the DSM_out pin.

The carrier signal is comprised of two distinct and separate signals. A Carrier High (CARH) signal and a Carrier Low (CARL) signal. During the time in which the modulator (MOD) signal is in a Logic High state, the DSM mixes the CARH signal with the modulator signal. When the modulator signal is in a Logic Low state, the DSM mixes the CARL signal with the modulator signal.

Using this method, the DSM can generate the following types of key modulation schemes:

  • Frequency Shift Keying (FSK)
  • Phase-Shift Keying (PSK)
  • ON-OFF Keying (OOK)

Additionally, the following features are provided within the DSM module:

  • Carrier Synchronization
  • Carrier Source Polarity Select
  • Programmable Modulator Data
  • Modulated Output Polarity Select
  • Peripheral Module Disable, which provides the ability to place the DSM module in the lowest power consumption mode
The figure below shows a simplified block diagram of the data signal modulator peripheral.
Figure 34-1. Simplified Block Diagram of the Data Signal Modulator