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CONTROLLERS

RAVITESH MISHRAASST. PROFESSOR

BCE,MANDIDEEP

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It is a special sequential machine.

It interpret system level control input

sequences.

Receives input from each component &

generate control signals for the system.

It becomes nervous centre for the system.

SYSTEM CONTROLLER

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1 Define purpose & role of system.

2 Define basic operation & limitations to handle.

3 Define time & frequency of system I/O.

4 Detail its sequential behaviour.

5 Develop MDS (Mnemonic Documented State) diagram.

6 Choose sysytem controller architecture & synchronizers.

7 Make state assignment.

CONTROLLER DESIGN PHASE

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IMPLEMENTATION OF CONTROLLER

1. RANDOM LOGIC2. Implemented with mealy or

moore machine similar to sequential circuits.

USING ROMNext state decoder & output decoder is replaced by ROM or PROM

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IMPLEMENTATION OF CONTROLLER (Cont.)

USING COUNTERS

Use counter in place of memory.

Any multimode counter can be used with specification

1) asynchronous clear 2) synchronous load 3) count enable

control

Qualities of counter

Count and branch conditionally and unconditionally.

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MICROPROGRAM CONTROLLERMicroprogrammed

Controller:Micro instruction is used & stored in contro memory when executed generazte controlSignals.Next Address Generator:Generate address of nextmicroinstruction.

Control Address Registration:

Specifies address ofmicroinstruction.

Control Memory:Stores the microinstruction.

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ADVANTAGES

1 Regular & computation independent

structure.

2 Change the Structure by reprogramming.

3 It replaces the bulky hardware.