CENG232 Logic Design Lab 4 Solved

1          Part 1: RGB Memory (40 pts)
In this part, you are expected to implement basic memories as Verilog modules. These modules will be used to apply masking operations to a given pixel of an image and save the resulting value to the memory. Illustration of the modules is provided in Figure 1.

 

Figure 1: Illustration of the modules.

1.1       RgbMask Module
This is the upper module, in which inputs and outputs of other modules are defined. The inputs of this module; RGBin, Mode, Address and Op are distributed to RgbRAM and MaskROM modules.

The pixel value, which will be given as input RGBin, consists of 3 color channels: Red, Green and Blue. Each of these channels contains 8 bits and has a range from 0 to 255. Illustration of RGBin is provided below:

RGBin (24 bits)
Red
Green
Blue
8 bits
8 bits
8 bits
Mode can be either Write(1) or Read(0).

4-bit Address input is used to point memory locations by both of the modules.

The details of masking operations (Op) are provided in Table 2.

RgbMaskModule has already been implemented by us; hence, you should not implement this module. MaskROM and RgbRAM modules will be implemented by yourselves.

1.2       MaskROM Module
This module basically contains 16 registers. Each register has a size of 8 bits, and stores a unique Mask value. The module returns the value of the register pointed by the given RomAddress as output RomDataOut. It works as a combinational circuit. That means it is not triggered by a clock pulse; it is triggered by RomAddress change. The values of ROM should be set as given in Table 1.

Address
Value (8 bits)
0
00000000
1
00001111
2
00011110
3
00110000
4
01010000
5
01100110
6
01101010
7
01111110
8
10000001
9
10100000
10
10100110
11
10111101
12
11000000
13
11010000
14
11010011
15
11100110
Table 1: ROM Structure

Use the following Verilog definition for the module:

module MaskROM (

input [ 3 : 0 ] RomAddress, output reg [ 7 :0 ] RomDataOut

) ;

1.3       RgbRAM Module
RgbRAM module is used to store/retrieve 24-bit RGB pixel values. In write mode(Mode=1), a specific mask operation(Op) is applied and the result is saved to the RamAddress location of the memory. In read mode(Mode=0) the 24-bit pixel value is retrieved from the RamAddress location of the memory.

Use the following Verilog definition for the module:

module RgbRAM (

input Mode, input              [ 3 : 0 ] RamAddress, input     [23:0] RamDataIn, input         [ 7 : 0 ] Mask, input        [ 2 : 0 ] Op, input CLK, output reg           [23:0] RamDataOut

) ;

1.3.1         Read Mode:

In Read Mode, when RamAddress value is given as i, the value stored in the ith index of the RgbRAM will be returned as output RamDataOut. No masking or write operation is conducted on the memory during this mode. This operation will be combinational. That means it is not triggered by a clock pulse; but triggered by the following events:

When Mode is changed from Write to Read, or

When the value of RamAddress is changed during Read mode.

Note: Initially, the values of all RAM registers will be 0 .

1.3.2         Write Mode:

In Write Mode, you will perform the requested masking operation (Op) on each of R, G and B channels of RamDataIn in the same clock cycle. After applying the operation, you will save the 24-bit result to RamAddress location of the memory. This procedure will be sequential, and it is triggered by the positive edge of the clock pulse.

Op values and their corresponding masking operations are provided in Table 2.

Op
Operation
000
Bitwise AND
001
Bitwise OR
010
Bitwise XOR
011
Add
100
Subtract
101
Increment
110
Decrement
111
Rotate Left
Table 2: Mask Operations

Detailed explanations and examples for the operations are provided below. Note that Mask is the value that comes from MaskROM. Also note that you should save the result of the operation to the RamAddress location of the memory.

Bitwise AND: You should perform AND operation between the Mask and each channel of RamDataIn.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
10100110
10000000
10000010
00000010
 
 
 
 
 
 
 
Bitwise OR: You should perform OR operation between the Mask and each channel of RamDataIn.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
10100110
10100111
11100111
11100110
 
 
 
 
 
 
 
Bitwise XOR: You should perform XOR operation between the Mask and each channel of RamDataIn.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
10100110
00100111
01100101
11100100
 
 
 
 
 
 
 
Add: You should add the Mask value to each channel of RamDataIn. The channel value cannot be greater than 255. Set result to 255 if the output of the addition is greater than 255.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
10100110
11111111
11111111
11101000
 
 
 
 
 
 
 
Subtract: The Mask value should be subtracted from each channel of RamDataIn. The channel value cannot be less than 0. Set the result to 0 if the output of the subtraction is less than 0.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
10100110
00000000
00011101
00000000
 
 
 
 
 
 
 
Increment: Increment each channel of RamDataIn by 1. The channel value cannot be greater than 255. As in Add operation, you should set the result to 255 if the output of the addition is greater than 255.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
not applied
10000010
11000100
01000011
 
 
 
 
 
 
 
Decrement: Decrement each channel of RamDataIn by 1. The channel value cannot be less than 0. As in Subtract operation, the result should be 0 if the output of the subtraction is less than 0.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
not applied
10000000
11000010
01000001
 
 
 
 
 
 
 
Rotate Left: Shift all the bits of each channel to the left by one. In addition, set the rightmost bit to the previous value of the leftmost bit.

RamDataIn (24 bit)
Mask (8 bit)
Result (24 bit)
10000001
11000011
01000010
not applied
00000011
10000111
10000100
 
 
 

2         Part 2: Gas Station (60 pts)
2.1      Problem Definition
In this part of the homework, you are asked to develop an entry system for a gas station. The system is summarized as follows:

1.     The following 2 types of fuel can be sold in the station:

(a)    Gasoline (0)

(b)   Diesel (1)

2.     There can be at most 6 fuel pumps in the station (there may be less than 6 pumps). Each fuel pump is dedicated to one type of fuel.

3.     The station may sell only one type of fuel or two types of fuel.

(a) There can be no gasoline pumps in the station. In this case, the number of diesel pumps can be 1 to 6. (b) There can be no diesel pumps in the station. In this case, the number of gasoline pumps can be 1 to 6.

(c) There can be both two types of fuel pumps in the station. In this case, the sum of the numbers of gasoline and diesel pumps should be at most 6.

4.     The system records status of 6 pumps with a single variable (pumpstatus). Each bit of pumpstatus corresponds to a fuel pump. 1 means the pump is available for a car to use and 0 means the pump is currently servicing a car or it is not added to the station. The order of the pump bits in the pumpstatus is as follows:

5.     The status lights show the status of each pump individually starting from the left-most light with gasoline pumps (if any). After the gasoline pumps are finished, the diesel pumps (if any) follow without any empty space.

(a) If there are gasoline pumps, they are represented by the left-most bits.

E.g. If the system has 1 gasoline pump and no diesel pumps then initial pumpstatus is 100000 where the left-most digit represents a gasoline pump.

pump status index
0
1
2
3
4
5
Fuel Type
G1
 
 
 
 
 
Led
LD7
LD6
LD5
LD4
LD3
LD2
(b)   If there are gasoline and diesel pumps, then corresponding bits of diesel pumps are located right after of the gasoline bits, E.g. If the system has 2 gasoline pumps and 3 diesel pumps then initial pump status is 111110.

pump status index
0
1
2
3
4
5
Fuel Type
G1
G2
D1
D2
D3
 
Led
LD7
LD6
LD5
LD4
LD3
LD2
(c)    If there are only diesel pumps, they are represented by the left-most bits. E.g. The system has no gasoline pumps and 3 diesel pumps then initial pumpstatus is 111000.

pump status index
0
1
2
3
4
5
Fuel Type
D1
D2
D3
 
 
 
Led
LD7
LD6
LD5
LD4
LD3
LD2
6.     The availability of each queue is recorded (isgasolinequeuenotfull, isdieselqueuenotfull). 1 means the queue is not full and there are available slots for new cars and 0 means the queue is full.

7.     A customer can demand at most 8 gallons of fuel (fuelamount). The system should give a warning

(invalidgasolinecar, invaliddieselcar) if a new car demands more than 8 gallons or demands no fuel (0 gallons).

8.     A fuel pump can fill 1 gallon of fuel in one unit of time.

9.     For each type of fuel (gasoline or diesel), there is a separate car waiting queue. If all of the pumps for the fuel type is busy, then the new car can wait in the queue of that fuel type.

10.   There can be at most 2 waiting queues; 1 for gasoline cars and 1 for diesel cars. If the station sells just one type of fuel, then there should be only one waiting queue.

11.   The waiting queues are first in first out (FIFO) queues. E.g. the first car entered the queue will use the empty pump first.

12.   Each waiting queue has a capacity of 8 cars. If a queue for a fuel type is full, then no new car can enter the station for this fuel type until there is a free space in the queue.

13.   The number of cars waiting in each queue is recorded (ncarsingasolinequeue, ncarsindiesel queue). When a new car enters the waiting queue or when a car leaves the queue to use a pump, the number of cars in that queue should be updated.

14.   The amount of fuel that is needed to fill the cars in the station is recorded (totalgasolineneeded, totaldieselneeded). This amount includes both the fuel demands of the cars waiting in the queue and remaining fuels to be filled by the pumps.

2.2     Simulation
There will be three modes in the system which are all synchronous:

1.   Setup Mode (1X):

(a)    This mode is used to set the number of gasoline pumps and diesel pumps.

(b)   This mode can also be used to reset the system and setup a new station if a simulation is already running.

(c)    In this mode, the waiting queues and all other recorded information should be set to their initial states. E.g. the queues should be empty after this mode.

(d)   If the total number of pumps ( diesel + gasoline ) is more than 6 or equal to 0, then the system should give a warning (invalidsetupparams). In this case:

Take no action.

Do not clear any data or reset the simulation.

The simulation may continue from where it’s left when the mode is changed back to simulation (00 or 01).

(e)    You must turn off 7-segment displays if there are no pumps for a fuel type.

Use the following values, the display implementation is provided in the Board232.v

Set ncarsin(gas|dsl)queue to 4'b1111 Set total(gas|dsl)needed to 8'b11111111

2.   Simulation Mode (00):

(a)    The setup must be done before running this mode. If no setup was done before this mode, then the system should take no action.

(b)   If setup was done, this mode is used to simulate the time. 1 unit of time passes in each clock.

(c)    The simulation works in the following order:

i.      If there are available pumps in the station, cars waiting in the queues move to empty pumps starting from the left-most pump of the corresponding fuel type.

More than one car may move from each queue to the pumps. If there are cars waiting in the queues, all available pumps must be used by them.

ii.    A new car may try to enter the station. It should be handled according to the specifications explained in the item 3.

iii.   All the pumps in the station service the cars for one unit time. Abdullah: ?

(d)   Each car using a pump is filled with 1 gallon of fuel. Therefore, the amount of fuel that is needed (totalgasolineneeded, totaldieselneeded) should be updated.

(e)    If a car is filled up, it leaves the station. In this case, the status of the pump should be updated to reflect the change.

(f)    If one or more gas pumps become empty, one unit of time is needed for waiting cars to leave the waiting queue and use the empty gas pumps.

(g)    A green status light (using pumpstatus) means the pumps is available for a new car. If the light is off, it means the pump is working or it is not added to the station during the setup.

3.   Car Entrance Mode (01):

(a)    The simulation continues in this mode.

(b)   A new car with a fuel amount and a fuel type tries to enter the station.

(c)    All actions must take the fuel type into consideration.

(d)   A new car may move to an empty pump if there are no cars in the queue.

(e)    If there are cars waiting in a queue, the new car must be added to the end of the queue.

(f)    If the car expects an out of range ([1..8]) fuel amount or the queue is full, invalidxxxcar warning light is set and the car is discarded.

(g)    All actions in the simulation mode must be done in this mode in the order described in the item 2.

4.   In case of an erroneous input (invalidgasolinecar, invaliddieselcar, invalidsetupparams) the system should set the warning bits. The warning message should be cleared in the next clock cycle unless another erroneous input is given again.


2.3        Input / Output Specifications
The inputs and outputs for Part 2 are presented in Table 3. The initial values are also given in Table 4.

Table 3: Input / Output Specifications

Name
Type
Size
mode
Input
2 bits
ngasolinepumps
Input
3 bits
ndieselpumps
Input
3 bits
fuelamount
Input
4 bits
fueltype
Input
1 bit
CLK
Input
1 bit
pumpstatus
Output
6 bits
isgasolinequeuenotfull
Output
1 bit
isdieselqueuenotfull
Output
1 bit
ncarsingasolinequeue
Output
4 bits
ncarsindieselqueue
Output
4 bits
totalgasolineneeded
Output
8 bits
totaldieselneeded
Output
8 bits
invalidgasolinecar
Output
1 bit
invaliddieselcar
Output
1 bit
invalidsetupparams
Output
1 bit
Table 4: Initial Values

pumpstatus
6'b000000
isgasolinequeuenotfull
0
isdieselqueuenotfull
0
ncarsingasolinequeue
4'b1111
ncarsindieselqueue
4'b1111
totalgasolineneeded
8'b11111111
totaldieselneeded
8'b11111111
invalidgasolinecar
0
invaliddieselcar
0
invalidsetupparams
0
2.4       FPGA Implementation
The input and output connections are provided in the supplemented Board232.v file. The mapping is provided in Table 5. In addition to the inputs and outputs given in Section 2.3, BTN1 works as a switch for the display modes between the numbers of cars and the fuel amounts. While the button is held pressed, the 7-segment displays will display the fuel amounts, otherwise they will display the number of cars in each queue. This part is implemented for you. Moreover, BTN3 works as another clock. You can press and hold it and the simulation will continue with successive clock ticks. The mapping between the items and the board is also provided in Figure 2.

Table 5: Input / Output Connections for FPGA board

Name
FPGA Board
Description
mode
SW[1,0]
(A)
2 right-most switches
ngasolinepumps
SW[7..5]
(B)
3 left-most switches
ndieselpumps
SW[4..2]
(C)
3 switches to the right of A
fuelamount
SW[7..4]
(D)
4 left-most switches
fueltype
SW[3]
(E)
The switch to the right of D
CLK
BTN[0]
(F)
The right-most button
pumpstatus
LD[7..2]
(G)
6 left-most status lights
isgasolinequeuenotfull
LD[1]
(H)
The status light to right of G
isdieselqueuenotfull
LD[0]
(I)
The status light to right of H
ncarsingasolinequeue
AN[2]
(J)
The second left-most 7-seg disp
ncarsindieselqueue
AN[0]
(K)
The right-most 7-seg disp
totalgasolineneeded
AN[3,2]
(L)
2 left-most 7-seg disp
totaldieselneeded
AN[1,0]
(M)
2 right-most 7-seg disp
invalidgasolinecar
AN[2] dot
(N)
The dot in 7-seg disp of J
invaliddieselcar
AN[0] dot
(O)
The dot in 7-seg disp of K
invalidsetupparams
AN[3..0] dots
(P)
4 dots in all 7-seg disp
Display mode switch
BTN[1]
(Q)
The button to the left to F
Press & hold clock
BTN[3]
(R)
The left-most button
 

Figure 2: Board figure with labels

 

Figure 3: 7-segment displays in detail