Unit1:
1. Show the block diagram of the hardware that implements the following register transfer
statement:
yT2: R2← R1, R1 ←R2
2. The outputs of four registers, R0, R1, R2. and R3, are connected through 4:1 line
multiplexer, which means that only one variable is equal to 1 at any given time, while the
other to 0. Draw a block diagram showing the hardware Implementation of the register
transfers.
3. Represent the following conditional control statements by two register transfer
statements with control functions:
If (P =I) then (R1 ←R2) else If (Q = I) then (R1← R3)
4. A digital computer has a common bus system for 16 registers of 32 bits each.
5. The following transfer statements specify a memory. Explain the memory operation in
each case.
a. R2←M[AR]
b. M[AR] ← R3
c. R5 ← M[R5]
6. Draw the block diagram for the hardware that implements the following statements:
x + yz: AR + ← AR + BR where AR and BR are two n-bit registers and x, y, and z are
control variables. Include the logic gates for the control function.
7. Using a 4-bit counter with parallel load and a 4-bit adder draw a block diagram that
shows how to implement the following statements:
x: R1 ← R1 + R2 Add R2 to R1
x 'y: R1 ← R1 + 1 Increment R 1
8. Register A holds the 8-bit binary 11011001. Determine the B operand and the logic
microoperation to be performed in order to change the value in A to:
A: 01101101
B. 1111 1101
9. An 8-bit register contains the binary value 10011100. What is the register value after an
arithmetic shift right? Starting from the initial number 10011 100, determine the register
value after an arithmetic shift left, and state whether there is an overflow.
10. A computer uses a memory unit with 256K words of 32 bits each. A binary instruction
code is stored in one word oi memory. The instruction has four parts: an indirect bit. an
operation code, a register code part to specify one of 64 registers, and an address part.
a. How many bits are there in the operation code, the register code part, and the
address part?
b. Draw the instruction word format and indicate the number of bits in each part.
c. How many bits are there in the data and address inputs in the memory?
11. The following control inputs are active in the bus system. For each case, specify the
register transfer that-will be executed during the next clock transition.
12. What are the two instructions needed in the basic computer in order to set the E flip-flop
to 1?
13. The content of AC in the basic computer is hexadecimal A937 and the initial value of E is
1. Determine the contents of AC, E, PC, AR, and IR in hexadecimal after the execution
of the CLA instruction.
14. The bus Is constructed with multiplexers.
a. How many selection inputs are there for each multiplexer?
b. What size of multiplexers are needed?
c. How many multiplexers are there in the bus?
15. Design an arithmetic circuit with one selection variable S and two n-bit data inputs A and
B. The circuit generates the following four arithmetic operations in conjunction with the
input carry Cin. Draw the logic diagram for the first two stages.
S Cin=0 Cin=1
—-------------------------------------------------------------------------------------
0 D=A+B D=A+1
1 D=A-1 D=A+B’+1
16. The content of the PC in the basic computer is 3AF (all numbers are in hexadecimal).
The content of AC is 7EC3. The content of memory at address 3AF is 932E. The content
of memory at address 32E is 09AC. The content of memory at address 9AC is 8B9F. a.
What is the instruction that will be fetched and executed next? b. Show the binary
operation that will be performed in the AC when the instruction is executed.
17. An instruction at address 021 in the basic computer has I = 0, an operation code of the
AND instruction, and an address part equal to 083 (all numbers are in hexadecimal). The
memory word at address 083 contains the operand B8F2 and the content of AC is A937.
Go over the instruction cycle and determine the contents of the following registers at the
end of the execute phase: PC, AR, DR, AC, and lR.
18. What is the difference between a microprocessor and a microprogram? Is it possible to
design a microprocessor without a microprogram? Are all microprogrammed computers
also microprocessors?
19. Explain the difference between hardwired control and microprogrammed control. Is it
possible to have a hardwired control associated with a control memory?
Define following: a) Micro-operation b) Micro-instruction c) microprogram d) micro-code
20. Using the mapping procedure described in class, give the first microinstruction address
for the following operation code: (a) 0010; (b) 1011; (c) 1111
21. Formulate a mapping procedure that provides eight consecutive microinstructions for
each routine. The operation code has six bits and the control memory has 2048 words.
22. Using 2 × 4 decoders and tri-state buffers, construct a bus system for four registers each
with four-bits.
