What are the three buses used in 8086 architecture?
Address bus, Data bus, Control bus
How wide is the address bus in 8086, and what memory range does it access?
20-bit wide; can access from 00000H to FFFFFH (1MB)
And its Uni-Directional (from MPU into the memory)
What is the difference in data bus width between 8086 and 8088?
8086: 16-bit data bus; 8088: 8-bit data bus
- Data bus is Bi-directional (information flows between MPU and I/O or Memory)
What is meant by multiplexed address/data lines in 8086?
The lower 16 bits (AD0–AD15) are used for both address and data, time-multiplexed to save pins.
What is the maximum memory size that can be accessed by 8086?
1 Megabyte (2²⁰ = 1,048,576 bytes)
How is the 1MB memory divided in the 8086 architecture?
Into four segments of 64KB: CS, DS, SS, and ES
How is a physical address calculated?
Physical Address = (Segment Register × 10h) + Offset
What is meant by Little Endian format?
In memory, the least significant byte is stored at the lower address.
Name the general-purpose registers in 8086.
AX, BX, CX, DX
What are the index and pointer registers?
SI (Source Index), DI (Destination Index), SP (Stack Pointer), BP (Base Pointer)
What is the role of the Instruction Pointer (IP)?
Points to the next instruction to be executed; combined with CS to form physical address
What are the two main units inside the 8086?
Execution Unit (EU) and Bus Interface Unit (BIU)
What is the function of the BIU?
Fetches instructions, reads/writes memory and I/O, manages the instruction queue.
What is instruction queue in 8086?
A 6-byte FIFO queue that prefetches instructions to speed up execution.
How does the stack work in 8086?
LIFO structure using SS:SP; grows downward in memory
What do PUSH and POP instructions do?
PUSH: Store register content to stack (SP-2); POP: Retrieve from stack (SP+2)
Name any four flags in the Status Register.
Carry (CF), Zero (ZF), Sign (SF), Overflow (OF)
What does the Zero Flag (ZF) indicate?
ZF = 1 if result of the last operation is zero
What are control flags in the status register?
Trap Flag (TF), Interrupt Flag (IF), Direction Flag (DF)
What are the two operating modes of 8086?
Minimum Mode (single processor) and Maximum Mode (multiprocessor system)
What is the difference between Minimum and Maximum Mode?
Minimum mode is used for standalone operation; Maximum mode is for systems with multiple processors, using a coprocessor like 8087.
Name any two control or status signals in 8086.
READY (wait states), HOLD (DMA), INTA (interrupt acknowledge)
What is the purpose of segment registers?
They point to memory segments: Code (CS), Data (DS), Stack (SS), Extra (ES)
