8086 is a 16bit microprocessor
Function of processor:
Control the entire circuit.
Execute the instruction.
Features of 8086:
1. Buses:
i. Address Bus : 8086 has a 20 bit address bus. Hence it can access 1 MB memory.The address range for this memory is 00000 H to FFFFF H.
ii. Data Bus : 8086 has a 16 bit data bus i.e it can access 16bit data in one operation. Its ALU and internal data registers are also 16 bits; hence 8086 is called as a 16 bit microprocessor.
iii. Control Bus : The control bus carries the signals essential for the various operations like Read, Write, etc.
2. 8086 supports Pipe-lining:
Pipeline is process of fetching the next instruction while executing the current instruction.
For eg.
Advantage of Pipe-lining:
Pipe-lining highly improves the performance of the system.
Disadvantage:
During execution (1st instruction) is the branch instruction occurs (i.e Jump/call) next instruction is invalid. Then instruction and pipe-lining gets fails.
For eg.
1 E 1 (if branch : go to 6)
2 F 2 Invalid
3
4
5
6 Fetching
Because of that instruction (go to 6 ) other instruction gets invalid from F 2 to F 5.
3. 8086 has 2 operating modes:
Advantage of Multiprocessor:
Ao Operation
0 0 R/W 16 bits from both bank
0 1 R/W 8 bits from Higher bank
1 0 R/W 8 bits from lower bank
1 1 No operation (Idle).
5. 8086 supports Memory Segmentation:
7.8086 has a 16 bit I/O address:
It can access 2^16 I/O ports (i.e. 64 KB I/O ports).
Because of that instruction (go to 6 ) other instruction gets invalid from F 2 to F 5.
3. 8086 has 2 operating modes:
Advantage of Multiprocessor:
- Speed of processing data is faster.
- Two programs can run simultaneously.
- The entire memory of 1 MB is divided into 2 Banks of 512 KB each.
- 8086 has a 16 bit data bus hence it should be able to access 16 bit data in one operation.
- To do so it needs to read from 2 memory location as one memory location carries one byte.
- However, if both these memory locations are i the same memory chip then the address bus will have to contain two addresses at the same time , which is impossible.
- To solve this problem, the memory of 8086 is divided into two banks provides 8 bit data.
- Therefore one banks contains all even addresses called "Even banks", while the other is called "Odd bank" containing all odd address.
Ao Operation0 0 R/W 16 bits from both bank
0 1 R/W 8 bits from Higher bank
1 0 R/W 8 bits from lower bank
1 1 No operation (Idle).
5. 8086 supports Memory Segmentation:
- Segmentation means dividing into logical components.
- Here the memory is divided into 4 segments (64 KB X 4) Code, Stack, Data and Extra Segment.
7.8086 has a 16 bit I/O address:
It can access 2^16 I/O ports (i.e. 64 KB I/O ports).
