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Project 4 A Simple Taximeter Design
Yuqi Wang & Suhuai Song
Introduction• This taximeter should be able to calculate the
“Fare” and “EXTRA” and then sum them to find out the total cost at the end.
• There are three modes:• Sleep mode• Mile charge mode• Time charge mode
Requirements• INPUTS:
• CLK: makes the code start working• VACANT: when this button on, the meter is off and all the
display will be off.• HIRED: when this button on, the meter is working.• TIME: when time is on, the time charge will be start.• SET_RATE+: set the rate higher manually.• SET_RATE-: set the rate lower manually.• TOTAL: when the button is on, allows the meter to
calculate the total fees the customer has to pay. Then assign the total fees value into “FARE” and at the same time “EXTRA” return to zero.
Requirements• OUTPUTS (7 Segment Display Number):
• RATE(7 bits): the fee of per miles. The default value is $3.
• FARE_2, FARE_1, FARE_0, FARE_d, FARE_dd (7 bits): the value of total miles fee. When the “TOTAL” button is on, the “FARE” should be showing total fee the customer should pay.
• EXTRA_2, EXTRA_d, EXTRA_dd: the value of total times charge. The default value is $1 per minutes.
Code Structure• Module Taximeter(input, output);• Input;• Output;• Always (posedge CLK) begin
• If (HIRED && ~VACANT) begin• If (miles <= 20 && SET_RATE+ == 0 && SET_RATE- == 0) begin // Condition 1• ….• End• If (miles > 20 && SET_RATE+ == 0 && SET_RATE- == 0) begin // Condition 2• ….• End• If (SET_RATE+ == 1 && SET_RATE- == 0) begin // Condition 3• ….• End• If (SET_RATE+ == 0 && SET_RATE- == 1) begin // Condition 4• ….• End• End
• If (~HIRED && VACANT) begin• …• End
• End
Code Structure• In each condition:
• If (TOTAL == 0) begin• // calculate the fare of total miles fee• End• If (TIME == 1) begin• // calculate the extra of total times fee• End • If (TOTAL == 1) begin• // calculate the fare of sum of the miles fee and times
fee and reset the all the extra value to 0.• End
Code Stucture• 7 Segment Decoder
• case(RATE) 4'b0000: rate = 7'b1111110; 4'b0001: rate = 7'b0110000; 4'b0010: rate = 7'b1101101; 4'b0011: rate = 7'b1111001; 4'b0100: rate = 7'b0110011; 4'b0101: rate = 7'b1011011; 4'b0110: rate = 7'b1011111; 4'b0111: rate = 7'b1110000; 4'b1000: rate = 7'b1111111; 4'b1001: rate = 7'b1111011; endcase
Simulation Results• HIRE = 0, VACANT = 1
Simulation Results• HIRED = 1, VACANT = 0, TIME = 1, SET_RATE+ =
0, SET_RATE- = 0, TOTAL = 0, miles = 15, times = 8
Simulation Results • HIRED = 1, VACANT = 0, TIME = 1, SET_RATE+ =
0, SET_RATE- = 0, TOTAL = 1, miles = 50, times = 8
Simulation Results• HIRED = 1, VACANT = 0, TIME = 1, SET_RATE+ =
1, SET_RATE- = 0, TOTAL = 1, miles = 50, times = 8
Simulation Result• HIRED = 1, VACANT = 0, TIME = 1, SET_RATE+ =
0, SET_RATE- = 1, TOTAL = 0, miles = 30, times = 5
Layout
Questions?
