Microinstruction Sequencing types , Fundamental Organization of MCU in English Hindi

This is Topic of Microprocessor 8086. Microinstruction Sequencing typesFundamental Organization of Microprocessor control unit (MCU) in Hindi and English first we are discus in Hindi after will be in stared in English here guven topic microinstruction sequencing block diagram, microinstruction sequencing ppt in hindi and English/

Microinstruction Sequencing types:
A micro-program control unit can be viewed as consisting of two parts:
1. Sequencing circuit that controls the generation of the next address.
2. The control memory that stores the microinstructions.

A micro-program sequencer attached to a control memory inputs certain bits of the microinstruction, from which it determines the next address for control memory. A typical sequencer provides the following address-sequencing capabilities:
1. Has a facility for subroutine calls and returns
2. Branches to an address as specified by the address field of the micro instruction.
3. Branches to a given address if a specified status bit is equal to 1.
4. Transfer control to a new address as specified by an external source (Instruction Register).
5. Increment the present address for control memory..
Depending on the current microinstruction condition flags, and the contents of the instruction register, a control memory address must be generated for the next micro instruction.

Fundamental Organization of MCU:- 
microinstruction sequencing

सामान्य प्रकार से Sequencing तीन प्रकार से की जाती हैं जो निर्देश में उपलब्ध मेमोरी एड्रेस पर निर्भर करती हैं

1. Single Address Field.:-
इस प्रकार की Sequencing में निर्देशों में मेमोरी एड्रेस का प्रयोग बहुत ही कम किया जाता है, क्योंकि यह क्रमबद्ध (Linear) Sequencing होती हैं, जिसमें प्रोग्राम काउंटर के मान को हर बार एक से increment किया जाता है।
microinstruction sequencing

इस प्रकार की Sequencing के सदैव अगला इंस्ट्रक्शंस Next मेमोरी एड्रेस पर ही उपलब्ध होता है

2. Two address field:-
इस प्रकार की Sequencing  में दो मेमोरी एड्रेस एक निर्देश में उपलब्ध होते हैं तथा दोनों के मध्य किसी एक का चयन होता है Condition Flag की अवस्था के आधार पर किया जाता है, यहां निर्देश में मेमोरी एड्रेस लिखे नहीं लेकर जाते हैं परंतु स्पष्ट होते हैं जैसे की :-
उदाहरण:-
Jump on zero (JZ) में दिया गया मेमोरी एड्रेस Zero flag के सेट होने पर अगले निर्देश में माना जाता है अथवा Jump on zero (JZ) के पश्चात लिखे गए निर्देश को अगला निर्देश मान लिया जाता है [linearly] इसको इंप्लीमेंट करने के लिए Multiplexer का प्रयोग किया जाता है जो  Condition Flag के आधार पर कार्य करता है.


3. Variable Address Field:-
बहुत ही जटिल प्रकार की Sequencing होती हैं जिसमें Condition flag अथवा अवस्थाओं के आधार पर निर्देशों का Sequencing Linear Condition हो सकता है तथा साथ ही साथ इस में offset तथा Index value भी प्रयोग में ली जाती हैं.

In English
There are three general techniques based on the format of the address information in the microinstruction:
1. Single Address Field.
2. Two Address Field.
3. Variable Format

Single Address Field:
Two-address approach is simple but it requires more bits in the microinstruction. With a simpler approach, we can have a single address field in the micro instruction with the following options for the next address.
Address Field.
Based on OPcode in instruction register.
Next Sequential Address.

Two Address Field:
The simplest approach is to provide two address field in each microinstruction and multiplexer is provided to select:
Address from the second address field.
Starting address based on the OP-code field in the current instruction.
The address selection signals are provided by a branch logic module whose input consists of control unit flags plus bits from the control partition of the micro instruction.


The address selection signals determine which option is selected. This approach reduces the number of address field to one. In most cases (in case of sequential execution) the address field will not be used. Thus the microinstruction encoding does not efficiently utilize the entire microinstruction.


Variable Format:
In this approach, there are two entirely different microinstruction formats. One bit designates which format is being used. In this first format, the remaining bits are used to activate control signals. In the second format, some bits drive the branch logic module, and the remaining bits provide the address. With the first format, the next address is either the next sequential address or an address derived from the instruction register. With the second format, either a conditional or unconditional branch is specified.

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