CSE370 Fall 99

Assignment 5

Distributed: 11/1/99

Due: 11/8/99

 

Reading:

Katz, Chapter 5 through 5.3.1, the rest of Chapter 5 is optional

Verilog Introduction: http://www.eg.bucknell.edu/~cs320/1995-fall/verilog-manual.html Recommend sections 2.2-2.7

Design Works Howto: http:370/98au/admin/Tools/DesignWorks/Verilog.html

 

 

Top-Down Design of a Bi-directional Collision Warning System.

 

In top-down design, it is not unusual to design and verify a system before the detailed design of some of its parts is complete. In this assignment, we will approximate that process for the Bi-directional Train Warning System of midterm infamy. The following steps constitute the basic top-down design process:

 

A.     Create a behavioral (high level language) model of the entire system based on the specification below. We are going to skip this step for now (nothing to turn in).

 

B.      Decide how to simplify the problem by breaking it into manageable sub-problems. In this case, please assume that you have decided to implement the bi-directional subsystem using the unidirectional warning system. The specification for the uni-directional warning system is the same as for the bi-directional warning system, except that we assume Train A is always further west than Train Z (nothing to turn in yet).

 

C.      Create and verify a behavioral model of the unidirectional subsystem for use in design and simulation of the complete bi-directional warning system. Most of the Verilog model is included below. Please complete the model and link it to a device called UniWarn in your library. Follow the attached instructions for doing this. Test your UniWarn device to your satisfaction, and turn in the completed Verilog model.

 

module UniWarn(a, b, c, x, y, z, warn);

// I/O Port Declarations

input a;

input b;

input c;

input x;

input y;

input z;

output warn;

// internal declarations

reg warn;

 

// behavioral model for UniWarn system

always @(a or b or c or x or y or z) begin

if (a && ~x) warn = 0;

if (~a && x) warn = 1;

if (~a && ~x) warn = ({b,c} > {y,z});

if (a && x) warn = ; // please fill in

// note that {b,c} is regarded as a 2-bit UNSIGNED

// number by Verilog

end

endmodule

 

D.      Design the bi-directional system using UniWarn device, and any other sub-systems that your think will be useful. You may use any parts from the primgate or primlog libraries to implement the system. Turn in the DW schematic for the system, showing all levels of hierarchy as needed, along with a description of the design concept, and an explanation for each element of the design. Also turn in the DW spreadsheet showing the inputs and verified expected outputs for each of the following cases:

 

Train A

Train Z

Speed

Pos

Speed

Pos

-3

0

+3

1

-3

1

+3

0

0

0

0

0

-2

2

-1

0

1

2

0

3

1

3

0

2

1

2

1

0

 

 

 

E. On paper, showing your work, complete the detailed design of the UniWarn sub-system using only the following hardware (hint: take a look at the Verilog model):

         One 4:1 multiplexor

         The PLA shown in the figure.

 

 


Appendix

 

Specification for the Bi-directional Collision Warning System

Train A and Train Z are on the same track. The velocity of each train is represented by a 3-bit 2s complement number from -3 to +3. The A and Z velocity inputs are {a,b,c} and {x,y,z} respectively. If the velocity is positive the train is traveling east, otherwise the train is traveling west. The position of each train is represented by a 2-bit unsigned number where 0 is furthest west and 3 is furthest east. The A and Z position inputs are {p,q} and {m,n}. The system issues a warning (W) whenever the current velocities and positions of train A and train Z will result in a collision assuming no future velocity changes. There is no need to issue a warning if the trains are going the same speed in the same direction. However, a warning should be issued if the two trains are in the same position.