General Release Specification — MC68HC05RC16

Section 9. Carrier Modulator Transmitter (CMT)

9.1 Contents

9.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

9.3 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

9.4 Carrier Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

9.4.1 Time Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

9.4.2Carrier Generator Data Registers (CHR1, CLR1,

CHR2, and CLR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

9.5 Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74

9.5.1 Time Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

9.5.2 FSK Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

9.5.3 Extended Space Operation . . . . . . . . . . . . . . . . . . . . . . . . .78

9.5.3.1 End Of Cycle (EOC) Interrupt . . . . . . . . . . . . . . . . . . . . .79

9.5.3.2 Modulator Control and Status Register (MCSR) . . . . . . .80

9.5.4Modulator Period Data Registers

(MDR1, MDR2, and MDR3) . . . . . . . . . . . . . . . . . . . . . .83

9.2 Introduction

The carrier modulator transmitter (CMT) module provides a means to generate the protocol timing and carrier signals for a wide variety of encoding schemes. It incorporates hardware to off-load the critical and/or lengthy timing requirements associated with code 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 disabled, certain CMT registers can be

MC68HC05RC16 — Rev. 3.0

 

General Release Specification

 

 

 

MOTOROLA

Carrier Modulator Transmitter (CMT)

67