Preload Count 0
Down Counter 0
=
0
Valid 0 Down Counter
Preload Valid 0
=
0
Clock 0
Reload
Reload
Compare and Control
Logic
Down Counter 1
Clock 1
Preload Count 1
Reload
Single
Sequence
Mode
Error (to ESM)
Reload
Done (to VIM)
Introduction
393
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Dual-Clock Comparator (DCC) Module
11.1 Introduction
The primary purpose of a DCC module is to measure the frequency of a clock signal using a second
known clock signal as a reference. This capability can be used to ensure the correct frequency range for
several different device clock sources, thereby enhancing the system safety metrics.
11.1.1 Main Features
The main features of each of the DCC modules are:
•
Allows application to ensure that a fixed ratio is maintained between frequencies of two clock signals
•
Supports the definition of a programmable tolerance window in terms of number of reference clock
cycles
•
Supports continuous monitoring without requiring application intervention
•
Also supports a single-sequence mode for spot measurements
•
Allows selection of clock source for each of the counters resulting in several specific use cases
11.1.2 Block Diagram
illustrates the main concept of the DCC module.
Figure 11-1. DCC Operation
