What are the differences between hardwired control design and microprogrammed control design?

Answer 1

A hardwired control unit has a processor that generates signals or instructions to be implemented in correct sequence. This was the older method of control that works through the use of distinct components, drums, a sequential circuit design, or flip chips. It is implemented using logic gates & flip flops. It is faster, less flexible & limited in complexity

A micro programmed control unit on the other hand makes use of a micro sequencer from which instruction bits are decoded to be implemented. It acts as the device supervisor that controls the rest of the subsystems including arithmetic and logic units, registers, instruction registers, off-chip input/output, and buses.

It is slower, more flexible & greater complexity

Answer 2

Hardwired control is a control mechanism to generate control signals by using appropriate finite state machine (FSM). Microprogrammed control is a control mechanism to generate control signals by using a memory called control storage (CS), which contains the control signals. Although microprogrammed control seems to be advantageous to CISC machines, since CISC requires systematic development of sophisticated control signals, there is no intrinsic difference between these 2 control mechanism.

Answer 3

Hardwired control is a sequential logic circuit or a finite state machine that generate a sequence of control signal in respone to the externally supplied instructions.

Where in microprogram control the control signal associated with operation are stored in special memory limit in visible by programmer as control words.

Answer 4

A hard-wired control system is what was first used in most areas. It uses either mechanical or electrical ways to control things.

For example, in a car the steering wheel is still a hard-wired system in that there is direct control of the tire angles, starting from the steering wheel. The steering wheel is connected to a shaft that directly transfers its rotation to another piece (often a rack-and-pinion gearbox), which then transfers the steering wheel's rotation into the front axle movement. The front axle is connected to each of the front wheels that then move with it. So, every bit of steering wheel rotation causes the front wheels to move by a fixed amount. Even Power Steering systems are still hardwired, since they only affect the boost (power) that is transmitted. The control is still direct, and proportional in the entire system.

A soft-wired control system is always digital - i.e. it has a computer (or sometimes a simpler table-driven calculator) with software. The software is designed to do the same thing that a hardwired control system would do, but it is also able to do very different things. In the car example above, a steering system that is soft-wired could determine the amount of turning that the steering wheel causes and make it depend on the speed. So when the car is going faster, it could reduce the "turnability" of the car to make it more stable. Or it could increase the turnability by large amounts when the car is moving very slowly or when it is in reverse - to help the driver maneuver in a parking lot. The behavior is not fixed and can depend on other "inputs" (e.g speed, brake pressure, throttle position, actual speed, weight being pulled by the car, etc). Another term for soft-wired control systems is "dynamic control systems" because the way they behave is "dynamic" and not fixed.

An example of a soft-wired control system is in today's fighter jets. Some of the best fighter jets today would not be able to fly with a hardwired control system. This is because these planes are naturally unstable when they fly - that means the plane would either wobble or stall or spin if they had hard-wired controls. No human pilot would be able to fly these planes - which is why we didn't have them earlier. In these planes today, their soft-wired control systems adjust flight surfaces very quickly (faster than a person could) and take many inputs quickly to calculate the best way to make the plane do what the pilot wants. In many ways, it's like flying a plane in a video game. The computer decides what the pilot wants to do, and it figures out the best way to make the plane do that. The flight stick is not controlling anything - it is just like the controller in a video game. It is only "asking" the computer to do something, and the computer decides how it will control the plane.

Soft-wired control systems are much more complicated, but they let machines do things that were not possible earlier. We can now build complex and almost animal-like robots today because of soft-wired controllers - remember the now ancient Furby toys (they were one of the first soft-wired toy pets). So even though soft-wired systems are harder to make, they make better things.