Test: Control Unit- 1

System bus is a single computer bus that connects the major components of a computer system, combining the function of a data bus to carry information, an address bus to determine where it should be sent and a control bus to determine its operation.

An interrupt alert the processor to a high-priority condition requiring the interruption of current code the processor is executing. Hardware interrupt are generated by hardware devices, when something unusual happned also called external interrupt.

Processor or processing unit is an electronic CKT which perform operations on some external source, usually memory or some data stream. Processor executes a set of machine language instructions.

To prevent signals from colliding on the bus, a controller prioritize access to memory by I/O channels and processors.

Buffers is a data area shared by hardware devices or program processes that operate at different speeds or with different sent of priorities.

Halt operation comes under control transfer.

Three states of bi-directional bus is input data to RAM, output data to RAM and high impedance.

Horizontal micro instructions have following attributes:
1. Long formats.
2. Ability to express a high degree of parallelism .
3 . Little encoding of the control information.

Since PLA is neither a hard-wired model nor a memory.
∴ We can say control unit with PLA as Hardwired or micro programmed control unit.

A micro-programmed control unit facilitates easy implementation of new instructions than hardwired.