Information given:
1) 2 X 8-bits input A and B
2) 1 X ?-bits function selector input
3) 1 X 8-bits output C
4) 1 bit overflow (designed as “flag O” )
Function selector are made up of:
1) A + B operation 7) A NOR B
2) A – Boperation 8) A XNOR B
3) A AND B 9) A RIGHT SHIFT (by) B
4) A OR B 10) A LEFT SHIFT (by) B
5) A XOR B 11) A CIRCULAR SHIFT L & R (by) B
6) A NAND B 12) Incremental of A + B
Explanation for function selector 12):
When input A + B , the output C will start from A A +1 A + 2 A +3 ... A+B
Show the incremental value from A to A + B using programming and the timing delay is 1sec
Summary of operation:
Display Input A Display Input B Display Output C LED
Timer
1 2 3 ON
4 5 6 OFF
7 8 9 RESET
0 A B ENTER
X X X
X X X
X X X
X X X
Keypad
1) The input A and B will have a 3-decimal display to represent the decimal values of the keyed-in 8-bits input
2) When input A is selected (by pressing A in the keypad) , pressing the value of input A will be displayed at the display input A after pressing “ENTER”.
3) Step 2 is the same for input B
4) After displaying input A and B, choose a function in the function selector to display output C at the display output C.
5) when an overflow is detected, the LED at display output C will be switched on.
6) for the function number 12th, Timer must display the timing delay of 1sec
Problems:
1) How many bits of function selector should be used? Explain why.
2) Design a full logic circuit diagram of this entire operation. Must show all the logic gates involved
Tips: ( must have Multiplexer , demultiplexer , decoder, encoder ,shift register, 7-segment display , memory(RAM or ROM) ,ALU , timer and other suitable logic circuit)
3) what is the typical operating voltage for this circuit? Frequency?
Extra question:
1) as the maximum value of decimal for 8-bits is 255, what would happen if a higher value of decimal is keyed-in? for example, if we key in 355 in the input A, what would be displayed in the output C? Describe the response of the circuit regarding to the input.
2) Say we want to key in a number “123” to input A , but we accidentally press 124 instead. By using “RESET” in the keypad, describe the operation of the circuit when the number “4” is reset to 3. Tips:(involve Shift register and Memory)
3) When a 3-bits input A is added to 3-bits input B, the addition may cause an overflow of 1 bit,causing the LED to be switched on.We wish to know the value of the overflow bit.Describe how do we display the overflow bit (0,1,2…9)?
Tips: use a set of LED to show the number of the overflow.when a LED is ON,the value is 1.when a led is OFF,the value is 0.use 4 LED
Decimal value
0 0 0 0 0
0 0 0 1 1
0 0 1 0 2
1 0 0 1 9
1 answer