Forum: FPGA, VHDL & Verilog Need Help:VHDL Model & Synthesis of Traffic Light Controller

von Jimmy C. (ryukifaiz)

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This is the first time i am exposed to VHDL , and i am currently no idea 
on doing my project, hopefully any expert here can help me and guide me 
on doing this ,thanks in advanced.

· Designing, Modeling and Simulation of Traffic Light Controller using 
· Verification of the functionality using a VHDL test bench, using 
qu(at)rtus II
from Altera.
· Synthesizing the verified VHDL Model of Traffic Light Controller
specifications using synthesis tool, qu(at)rtus Integrated System (QIS) 
Altera for structural simulation.
· Downloading the designed codes into FPGA board for verifying the 
(Traffic Light Controller) functionality.

A. Design Specifications
Traffic lights are integral part of modern life. Their proper operation 
can spell the
difference between smooth flowing traffic and four-lane gridlock. Proper 
entails precise timing, cycling through the states correctly, and 
responding to outside
inputs, like walk signals.
The controller to be designed controls the traffic lights of a busy 
highway (HWY)
intersecting a side road (SRD) that has relatively lighter traffic load. 
Figure 1 shows
the location of the traffic lights. Sensors at the intersection detect 
the presence of cars
on the highway and side road. The Figure implies that both the highway 
and side
roads offer single lanes for traffic in each direction. Both roads have 
ordinary (Red,
Yellow, Green) signal lights. The intersection is fitted with a sensor.

B. Finite-state machine specifications
The traffic light controller works in the following way.
1. The lights controller makes use of car sensors at the intersection of 
the side road
with the highway, to sense presence of cars.
2. The lights controller makes use of three timers: a 60 seconds timer 
(T60), a 30
seconds timer (T30), and a 10 seconds timer (T10). Once a trigger signal 
is applied
to a timer, the timer output is zero and becomes 1 after the programmed 
period. For example, upon reset, the T30 timer output is '0' and will 
become '1' after
30 s have elapsed and stays '1' until reset by the controller.
3. Pedestrians can use the intersection by pressing buttons and 
debouncing switches.
Pedestrians will need to cross the highway only since crossing the side 
road is
assured most of the time.
4. HWY lights remain green as long as there are no cars triggering the 
SRD sensors.
5. When HWY lights have been green for a minimum of 60 seconds, a car on 
may cause HWY lights to cycle through yellow to red states.
6. Meanwhile, SRD lights will turn green and remain green for a minimum 
of 30
seconds. Further application of SRD sensors beyond the 30 seconds will 
SRD to remain green for a maximum of 60 seconds.
7. SRD lights will cycle through yellow and red states and HWY lights 
will then turn
8. The lights stay yellow for 10 seconds.
9. Each traffic post has three lights GREEN, YELLOW and RED.
10. In the default state, HWY lights show GREEN and SRD lights show RED.

C. Traffic light FSM Interface signals
The FSM to the traffic lights controller has the input signals shown in 
Table 1. The
controller has the output signals shown in Table 2.

D. Requirements
In this project, you are required to design, model and simulate the 
machine for the traffic light controller.
1. Draw the traffic-light controller as an icon indicating the I/O 
control signals.
2. Draw a block diagram for the traffic lights controller indicating 
clearly the main
system blocks and interface signals.
3. Draw a Mealy-style state diagram, which covers all legal state 
transitions of the
4. Use a two- or three-process FSM VHDL coding style. Make sure you have
adequate and clear comments in your code.
5. Provide a table indicating all the input and output signals of the 
traffic lights
controller and the traffic lights FSM.
E. Simulations
The VHDL code of traffic light controller will be simulated using 
qu(at)rtus II software
from Altera. Different corner cases were tested by writing a test bench. 
The sub
modules like the counter, register and multiplexer were written 
separately and also
tested separately by test benches. Behavioural Simulation of modules 
will be
represented in Timing waveform.
F. Synthesis
The verified VHDL modules then will be synthesized using synthesis tool, 
QIS from
Altera. Structural simulations will be carried out in QIS and will be 
compared with
behavioural simulations using the same test bench. You will present the 
Transfer Level (RTL) and Technology views of a Traffic Light Controller.

G. Downloaded into FPGA demo Board:
Finally, you will download your designed codes into the target 
technology, Field
Programmable Gate Array (FPGA) to verify the Traffic Light Controller 
with higher operating frequency. Noted that you will use FPGA board 

Figure 1, Table 1 and Table 2 in the attachment below

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von The hard way (Guest)

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> This is the first time i am exposed to VHDL
I can't believe that your teacher gives you this exercise without any 
previous information about VHDL. If so, you will have a demanding task 
in front of you...

So why not taking a book about VHDL and starting with the definition of 
a entity? All the input and output signals are given.
Next step will be to implement the timers.
After that the handling of the traffic light states will be implemented.
And finally the triggering from the sensors and buttons can be 

Most important: Divide the task in small steps.

von omran (Guest)

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simply to start designing and coding your design you need

to draw a finite state machine fsm then the code is just just like any 
code  in fsm.

start by knowing the fsm which should be done by your doctor or 

note that if you use the a hdl compiler you can genetate the code just 
by drawing the fsm using the compiler.

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