Information

Chapter 38
Carrier Modulator Transmitter (CMT)
38.1 Introduction
NOTE
For the chip-specific implementation details of this module's
instances see the chip configuration chapter.
The carrier modulator transmitter (CMT) module provides the means to generate the
protocol timing and carrier signals for a wide variety of encoding schemes. The CMT
incorporates hardware to off-load the critical and/or lengthy timing requirements
associated with signal generation from the CPU, releasing much of its bandwidth to
handle other tasks such as:
• Code data generation
• Data decompression, or,
• Keyboard scanning
. The CMT does not include dedicated hardware configurations for specific protocols, but
is intended to be sufficiently programmable in its function to handle the timing
requirements of most protocols with minimal CPU intervention.
When the modulator is disabled, certain CMT registers can be used to change the state of
the infrared output (IRO) signal directly. This feature allows for the generation of future
protocol timing signals not readily producible by the current architecture.
38.2 Features
The features of this module include:
• Four modes of operation:
• Time; with independent control of high and low times
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 839