Task 4-1: Build the Brainless Central Processing Unit
Include a picture of your Logisim Brainless Central Processing Unit circuit here:
Figure 1. Brainless Central Processing Unit JCC

Task 4-2: Test and Control the Brainless Central Processing Unit
Perform the testing procedures outlined in the laboratory manual and fill in the blanks below. (Note that these questions appear in the text of the laboratory manual.)
· Record the first number placed on the data bus here: 5
· What do the following three switches need to be set to in order to perform the pass-through operation? /~A_Only = 0 /~Invert= 1 Logic/~Arith= 0
· Enter the second number you entered into the data bus here: 2
· What do the following three switches need to be set to in order to perform the ADD operation? /~A_Only = 1 /~Invert= 1 Logic/~Arith= 0
· Write down the number that appears in the accumulator here: 7
Describe other numerical additions and other operations you checked in order to verify your brainless CPU here: I repeated the additions several times using 3, 4 and 1 and toggled through several times till I got the correct addition.
After you are convinced your circuit is working properly, remove the 4-bit binary keyboard and set the ACC to Data Bus pin to 1. Did the output of the accumulator appear on the data bus? Yes.
How does the output of the ALU change? It changed to Hex E.
If the 4-bit binary keyboard was not removed and the ACC to Data Bus switch is set to 1, what would you expect to see displayed in the hex digit display attached to the data bus?
I expect to see whatever is supplied to the data bus in hex display.
Add the 4-bit binary keyboard back into your circuit and observe the hex digit display on the data bus for various keyboard values. Is the value on the hex digit display what you expected? Yes.
Explain Only 1 signal is being allowed to enter the buffer at a time. Therefore, the buffer is receiving only the output of the register.
Why do you think the register at the output of the ALU is called the ‘accumulator’? Because it stores data that passes through the ALU, it provides a feedback path tho the B input of the ALU and because it can store intermediate arithmetic or logic results.

Test your circuit and record the results in Table 1. Include a picture of your Logisim addressing logic circuit testing set up.
Figure 3. Testing Addressing Logic JCC

 Table 1 A (4-bit binary) Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7 0000 1 0 0 0 0 0 0 0 0001 0 0 1 0 0 0 0 0 0010 0 1 0 0 0 0 0 0 0011 0 0 0 1 0 0 0 0

Task 4-4: Build a 4-Bit ROM Memory Cell
Include a picture of your Logisim 4-bit ROM circuit here:
Figure 4. 4-bit ROM memory cell JCC
Test your circuit and record the results in Table 2. Include a picture of your Logisim 4-bit ROM circuit testing set up.
Figure 5. Testing 4-bit ROM memory cell JCC

 Table 2 A (4-bit binary) Read Memory Select Y (Data Bus) 0001 1 1 1 0101 1 1 5 1000 1 1 8 1000 0 1 X 1000 1 0 X 1000 0 0 X

Task 4-5: Build 4-Bit Output Port
Include a picture of your Logisim 4-bit output port circuit here:
Figure 6. 4-bit output device JCC
Test your circuit and record the results in Table 3.

 Table3 Data Bus (4-bit binary) Write Memory Select Q 0001 1 1 1 0010 0 1 Last Q 0011 1 0 Last Q 0011 0 0 Last Q 0011 0 0 0 0011 1 0 0 0011 1 1 3 0001 0 0 0

Task 4-6: Build the 4-Bit RAM Cell
Include a picture of your Logisim 4-bit RAM circuit here:
Figure 7. 4-bit RAM JCC
Test your circuit and record the results in Table 4. Include a picture of your Logisim 4-bit RAM circuit testing set up.
Figure 8. Testing 4-bit RAM JCC

 Table4 Data Bus (4-bit binary) Write Memory Select Read Q {between register and buffer} Data Bus {after buffer} 0110 1 1 1 6 6 0110 0 1 1 6 6 0110 1 0 1 6 – 0110 0 0 1 6 – 0110 0 0 0 6 – 0101 1 1 1 5 5

Task 4-7: Build the Brainless Microprocessor
Include a picture of your Logisim brainless microprocessor circuit here:

Task 4-8: Testing and Controlling the Brainless Microprocessor
Follow steps 1 through 3 outlined in the laboratory manual to test your brainless microprocessor circuit. List in Table 5 the control lines you needed to control to store the accumulator (ACC) to

RAM. (If the control line value has no impact, place a dash ‘-‘ in the value column).

 Table5 Control line Value 4-bit binary keyboard (Address Bus) Write 0 Read 1 ACC to Data Bus 0 Load ACC 1 /~A_Only 0 /~Invert 0 Logic/~Arith 1

Describe any other tests that you performed. NOTE: the laboratory manual gives you a minimum set of items to test: __________________________________________________________________________
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Table 6 is an example, for the ADD command, of how to fill out tables to record the values of the control lines during every clock cycle.

 Table6 Instruction [ Add operand to Accumulator (ACC) ] Control Line Value 4-bit Binary Keyboard (Address Bus) Address of operand Write 0 Read 1 ACC to Data Bus 0 Load ACC 1 /~A_Only 1 /~Invert 1 Logic/~Arith 0

For all of the instructions you performed (i.e. Subtract, Load ACC, etc.) record the values of the control lines during every clock cycle in Table 7Table 8and Table 9.

 Table7 Instruction [Subtract operand from ACC ] Control Line Value 4-bit Binary Keyboard (Address Bus) 3 Write 1 Read 1 ACC to Data Bus 0 Load ACC 1 /~A_Only 1 /~Invert 1 Logic/~Arith 0

 Table8 Instruction [Load ACC with operand] Control Line Value 4-bit Binary Keyboard (Address Bus) 3 Write 1 Read 1 ACC to Data Bus 1 Load ACC 1 /~A_Only 0 /~Invert 1 Logic/~Arith 1 Instruction[AND operand with ACC] Control Line Value 4-bit Binary Keyboard (Address Bus) x Write 0 Read 1 ACC to Data Bus 0 Load ACC 0 /~A_Only 1 /~Invert 0 Logic/~Arith 1 Instruction[ Store ACC to RAM] Control Line Value 4-bit Binary Keyboard (Address Bus) X Write 0 Read 1 ACC to Data Bus 1 Load ACC 0 /~A_Only 1 /~Invert 1 Logic/~Arith 1

 Table 9 Instruction[ Not (operand) to ACC] (1’s complement) Control Line Value 4-bit Binary Keyboard (Address Bus) 3 Write 1 Read 0 ACC to Data Bus 0 Load ACC 1 /~A_Only 1 /~Invert 0 Logic/~Arith 0 Instruction[ Negate(operand) to ACC] (2’s complement) Control Line Value 4-bit Binary Keyboard (Address Bus) 3 Write 1 Read 0 ACC to Data Bus 0 Load ACC 1 /~A_Only 0 /~Invert 0 Logic/~Arith 1

Task 4-10: Build the Controller Circuit
Include a picture of your Logisim controller circuit here:

Task 4-11: Build the Complete Microprocessor Circuit
Include a picture of your Logisim complete microprocessor circuit, with controller, here:

Write the program given in your laboratory manual into the appropriate memory locations. Observe the operation of each step of your program (i.e. observe the values of the control lines and record whether data is being moved properly according to those control line settings). Did you get an 8 stored into the accumulator with you initial test?______
If not, what error(s) did you find during your debugging process?________________________________
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Use Table 10and Table 11to enter your values into the microinstruction definition table for each of the four instructions asked for in the laboratory manual. Be sure to label the name of each and every instruction.

 Table10 Instruction Opcode 3 4 Pres. State 00 01 02 03 00 01 02 03 Description Pin number Next State Bits 1-0 Load IR 2 Write 3 Read 4 ACC to Data Bus 5 Load ACC 6 Load MAR 7 Use PC 8 /~A_only 9 /~Invert 10 Logic/~Arith 11 X 12 X 13 X 14 X 15 HEX equiv

 Table11 Instruction Opcode 5 6 Pres. State 00 01 02 03 00 01 02 03 Description Pin number Next State Bits 1-0 Load IR 2 Write 3 Read 4 ACC to Data Bus 5 Load ACC 6 Load MAR 7 Use PC 8 /~A_only 9 /~Invert 10 Logic/~Arith 11 X 12 X 13 X 14 X 15 HEX equiv

Test your instructions by writing and executing programs. Record at least four programs and the output of each program in tables like that of Table 12.

 Table12 Program #0 ( Example: ADD = 3+5) Address Value Operation (In English) 0 0 The ‘Load ACC’ Opcode 1 3 The number ‘3’ to be loaded into the Accumulator 2 1 The ‘Add to ACC’ Opcode 3 5 The number ‘5’ to be added to the Accumulator 4 2 The ‘Stop’ Opcode What was the final output of your program? ___8__ Was the program successful? YES_ If not what error(s) did you find in your circuit?

 Program # ( ) Address Value Operation (In English) What was the final output of your program? _____ Was the program successful? Yes or No_ If not what error(s) did you find in your circuit?

Fill in the following two tables for your invented instruction.

 Instruction Opcode 7 Pres. State 00 01 02 03 00 01 02 03 Description Pin number Next State Bits 1-0 Load IR 2 Write 3 Read 4 ACC to Data Bus 5 Load ACC 6 Load MAR 7 Use PC 8 /~A_only 9 /~Invert 10 Logic/~Arith 11 X 12 X 13 X 14 X 15 HEX equiv

 Program # ( ) Address Value Operation (In English) What was the final output of your program? _____ Was the program successful? Yes or No_ If not what error(s) did you find in your circuit?

Simulation Lab 4: Lab Report Grade Sheet

 Name: