27 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 MDOUT 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.
