Microprocessor and Electronics Question Answer 2016.
1. Which type of architecture 8085 has?
8085 has Von Neumann architecture. It was derived after the name of mathematician
John Von Neumann. It’s having 16 address bus and 8 bit data bus.it can access 2^16
individual memory location.
2. How many memory locations can be addressed by a microprocessor with 14 address
3. 8085 is how many bit microprocessor?
8 bit as its data bus is 8 bit.
4. Why is data bus bi-directional?
As it has to carry data from mp to external device or the reverse. (?)
5. What is the function of accumulator?
This register is used to store 8-bit data and to perform arithmetic and logical operations.
The result of an operation is stored in the accumulator.
6. What is flag, bus?
The ALU includes five flip-flops, which are set or reset after an operation according to
data conditions of the result in the accumulator and other registers. They are called
Zero(Z), Carry (CY), Sign (S), Parity (P), and Auxiliary Carry (AC) flags. For more
details on flags see Q14.
Typical system uses a number of busses, collection of wires, which transmit binary
numbers, one bit per wire. A typical microprocessor communicates with memory and
other devices (input and output) using three busses: Address Bus, Data Bus and
The Address Bus consists of 16 wires, therefore Its “width” is 16 bits. A 16 bit Address
bus can identify 2^16=65536 memory locations i.e. 0000000000000000 up to
1111111111111111. Because memory consists of boxes, each with a unique address, the
size of the address bus determines the size of memory, which can be used. To
communicate with memory the microprocessor sends an address on the address bus, e.g.
0000000000000011 (3 in decimal), to the memory. The memory the selects box number
3 for reading or writing data. Address bus is unidirectional, i.e. numbers only sent from
microprocessor to memory, not other way.
Data Bus: carries ‘8-bit data’, in binary form, between μP and other external units, such
as memory. The Data Bus typically consists of 8 wires. Data bus used to transmit “data”,
i.e. information, results of arithmetic, etc, between memory and μP. Bus is bi-directional.
Size of the data bus determines what arithmetic can be done. If only 8 bits wide then
largest number is 11111111 (255 in decimal). Data Bus also carries instructions from
memory to the microprocessor. Size of the bus therefore limits the number of possible
instructions to 256, each specified by a separate number.
It is a group of various single lines used to provide control and synchronization signals.
μP generates different control signals for different operations. These signals are used to
identify the device with which the μP wants to communicate.
8. Why are program counter and stack pointer 16-bit registers?
Because SP points to the beginning of stack memory (LXI SP 8000H) which is 16-bits.
Also PC points to the memory locations (16-bits) of the instructions to be executed to
maintain the proper sequence of execution of program.
9. What does it mean by embedded system?
A specialized computer system that is part of a larger system or machine. Typically, an
embedded system is housed on a single microprocessor board with the programs stored in
ROM. Virtually all appliances that have a digital interface like watches, microwaves,
VCRs, cars etc utilize embedded systems. Some embedded systems include an operating
system, but many are so specialized that the entire logic can be implemented as a single
10. What are the different addressing modes in 8085?
Register:- Data is provided through the registers. Or operand is only register(s). Example:
MOV Rd, Rs.
Register indirect:- Operand M or register pair. Example: MOV A,M; LDAX B; STAX D;
MVI M,32H (exception for immediate addressing mode).
Direct:- Operand 8-bit port address or 16-bit memory address. Example: IN 84H, OUT
84H, all CALLs.
Immediate:- Instruction having the letter I. Or immediate data to the destination provided.
Also all jump instructions as the meaning is jump immediately. Example MVI M, 2H;
ADI 47H; LXIH 2050 (exception for direct addressing mode).
Implicit:- No operand. Example: XCHG.