What is microprocessor? Draw an internal block diagram of a register based microprocessor
and explain its operations. .
Microprocessor : With the advent of semiconductor technology, it is possible to integrate the CPU in a single. chip. The result is the microprocessor. Metal oxide semiconductor (MOS) technology is typically used to fabricate the standard off-the-shelf microprocessors. The microprocessor is comprised of a register section, one or more ALUs and a control unit.
Execution Unit ( EU ) BUS INTERFACE UNIT ( BIU )
Figure-1 : Internal block diagram of register based microprocessor 8086.
Figure-1 shows a block diagram of a register based microprocessor '8086. The 8086 is internally divided into two separate functional units :
i) Bus Interface Unit (BIU)
ii) Execution Unit (EU)
These two units function .independently. They are described below :
i) Bus Interface Unit BIU : this unit fetches instructions, reads data from memory and ports,
and writes data to memory and I/O ports. The BIU interfaces the 8086 to the outside world. It contains
and writes data to memory and I/O ports. The BIU interfaces the 8086 to the outside world. It contains
· Instruction pointer
· Instruction queue : The BIU's instruction queue is a First-In-First-Out (FIFO) group of registers in
Which up to six bytes of instruction code are prefetched from memory ahead of time.
® Address generation bus control circuitry : It provides functions such as fetching and queuing of instructions, and bus control. It generates all the bus control signals such as read and write signals for memory and I/0.
4, Segment registers The BIU has four (CS, DS, SS, ES)16-bit segment registers. The segments can be contiguous, partially overlapped, fully overlapped. or disjoint.
Execution unit : The EU decodes and executes instructions. It consists of the following
· A decoder in the EU control system translates instructions the .
· The EU has a 16-bit ALU for performing arithmetic and logic operations.
