Modeling Counters and Timers in Embedded MATLAB

Implementing various kinds of counters like Johnson, Gray, Mod counters in Embedded MATLAB.

Description

(Developed using R2007b)

Timers and counters are essential elements in hardware design. A timer can be used to measure elapsed time and a counter is used to count number of external events in hardware circuits.

This demo shows how to build timers and counters in Embedded MATLAB. The attached model contains implementations of the following counters.

 Gray Counter
 Johnson Counter
 Mod-N Counter
 Up Down Counter (With enable)
 Preset Clear Counter
 Call Count Detector
 
Gray Counter:

Gray code is a binary numeral system where two successive values differ in only one digit. Gray codes are widely used to facilitate error correction in digital communications such as digital terrestrial television and some cable TV systems. A 4bit gray code counter has the following binary sequence as its output.

0000
0001
0011
0010
0110
0111
0101
0100
1100
1101
1111
1110
1010
1011
1001
1000

Johnson Counter:

A ring counter is a type of counter composed of a circular shift register.
The output of the last shift register is fed to the input of the first register.
A Johnson counter is also called as a walking ring counter wherein the output of the last shift register is inverted and fed back to the input of first shift register. A 4bit johnson counter has the following binary sequence as its output.

0000
0001
0011
0111
1111
1110
1100
1000
0000

Modulo N Counter:

The total number of stable states a counter has indicates its MODULUS. A Mod3 counter has the following binary sequence as its output.

000
001
010
011
100
101
110
111

• Required Products: Simulink; Fixed-Point Toolbox
• MATLAB release: MATLAB 7.4 (R2007a)

[murali raju]