BASIC MICROPROCESSOR – SOFTWARE ARCHITECTURE OF 8088/8086

BUS INTERFACE UNIT & EXECUTION UNIT

8086/8088 ARCHITECTURE

Contains two parts:1. BIU (Bus Interface Unit)2. EU (Execution Unit)

BIU (BUS INTERFACE UNIT)

Interface to the outside world (connect to external devices)

Fetches instructions, reads and writes data

Queue instructions and generate address

BIU (BUS INTERFACE UNIT) CONT.

BIU contains:1. Internal communication registers2. Address generator3. Bus control logic4. Instruction queue

BIU (BUS INTERFACE UNIT) CONT.

Registers in BIU:1. CS – Code Segment Register2. DS – Data Segment Register3. SS – Stack Segment Register4. ES – Extra Segment Register5. IP – Instruction Pointer

EU (EXECUTION UNIT)

Decodes and executes the instructions EU contains:1. ALU2. Status and control flags3. General purpose register4. Temporary register

EU (EXECUTION UNIT) CONT.

Registers in EU:1. AX – Accumulator2. BX – Base Register3. CX – Count Register4. DX – Data Register

EU (EXECUTION UNIT) CONT

Registers in EU: (cont.)5. SP – Stack Pointer6. BP – Base Pointer7. SI – Source Index Register8. DI – Destination Register