Tutorial By Namitha

 

8051 MICROCONTROLLER & 8051 PROGRAMMING  

MEMORY INTERFACING            Communication between processor and memory is known as interfacing with memory (RAM or ROM) memory access possible by using Memory Read signals and Memory write signals. System is associated with different memory chips ,so processor need to properly fix one among them for performing memory access operations. So need a chip selection signal for selecting a memory chip properly . All these signals are generated by a device for supporting memory access operation is known as memory interfacing unit .

   

 

Dependency Preserving Decomposition  If we decompose a relation R into relations R1 and R2, All dependencies of R either must be a part of R1 or R2 or must be derivable from   FD’s of R1 and R2 .    Relation R is decomposed in to R1 and R2 with FDs F1 and F2 respectively  ,  if the decomposition is dependency preserving then F1 U F2 =F                                                and so           ( F1 U F2 ) + =F+

Normalization is the process of minimizing redundancy and eliminating anomalies from a relation or a set of relations.  Decomposition of a relation is done when a relation is not in required normal form .   We can decompose a relation into two or more relations if decomposition is lossless join as well as dependency preserving.  Upto 3rd normal form both of these decomposition properties we need to preserve.  Given a relation R after decomposing R into R1 and R2  , If R1 join R2 =R ,then the decomposition is said to be lossless join decomposition . If R1 join R2 is ⊃ R ,then the decomposition is said to be lossy decomposition .

               In the microprogrammed control units all the control signals associated with microoperations are stored in special memory called control memory .           Set of control signals that cause microoperations to occur is called microinstructions .           Micro-programmed control unit can be classified into two types based on the type of Control Word(microinstructions) stored in the Control Memory .  Horizontal micro-programmed control unit   Vertical micro-programmed control unit In  Horizontal micro-programmed  control unit, the control signals are represented in the decoded binary format .                     ‘n ’ control signals require n bit encoding i.e., 1 bit/CS .  In  Vertical micro-programmed   control unit, the control signals are repres...

A digital computer consists of CPU , a memory and I/O devices . CPU can be classified into two distinct but interactive fu nctional units    1)  Processing section (Processor)                               2) Control Section Microprogram sequencer is a convenient element for constructing a microprogram control for CPU .  Microprogrammed Computer consists of a  Memory unit ,two processor unit , a microprogram sequencer ,a control memory and few other digital functions . The memory unit stores the instructions and data supplied by the user through an input device .

A microprogram control unit consists of two parts : 1 ) Control Memory that stores the microinstructions 2) Associated circuits that control the generation of the next address . The address generation part is sometimes called a microprogram sequencer ,since it sequences the microinstructions in control memory .   T ypical sequencer provides the following address-sequencing capabilities : 1.Increments the present address for control memory .    Sequential access: The content of address register of the control memory (CAR) is    incremented after execution of each micro-instruction . 2. Branches to an address as specified by the address field of the microinstruction. 3 . Branches to a given address if a specified status bit equal to 1. 4.Transfer control to a new address as specified by an external source .   The external address transfers control to the first microinstruction in a microprogram . 5 .Support subroutine call ...

Control Memory In a micro-program control, the control variables that initiate micro-operations are stored in memory called control memory. •The control memory is a ROM, since the control sequence is permanent and needs no alteration. Micro instructions The word stored in the control memory are micro-instructions. Each micro-instruction specifies one or more micro-operations for the components in the system. 

Normalisationis a process of organizing the data in database to avoid data redundancyand anomalies . We have different levels of normal forms 1st,2nd, 3rd , BCNF ,4th,5th etc . A relation is always specified with its highest normalization level . First Normal Form defines that all the attributes in a relation must have atomic values . Second Normal Form is based on the concept of fully functional dependency . To be in second normal form, a relation must be in First Normal Form and every non-prim attributes are fully functionally dependent on any of the candidate keys. A relation is in 3rd normal form , 1)It must be in 2NF 2)Nonprime attributes should not be transitively dependent on candidate keys. For a relation to be in Boyce-CoddNormal Form (BCNF  or 3.5 NF) , 1.It should be in theThird Normal Form. 2.And, for any dependency X→ Y, X must be asuper key. Stronger version of 3NF .

A minimal cover of a set of FDs F is a minimal set of functional dependencies F min  that is equivalent to F. There can be many such minimal covers for a set of functional dependencies F. Steps to derive  minimal cover for  a FD set . 1)Right Hand Side (RHS) of all FDs should be single attribute . 2)Eliminate redundant functional dependencies if any . Given relation R(A,B,C)    and      FDs : {  AB -> C, C -> A }    FDmin ={AB à C}   ,here C-->A is   redundant dependency  3)Remove redundant attribute on LHS if any .  Consider  FD ,  AB -> C              If AB+ = A+  we can say B is redundant  then reduce to  A à C              If AB+ =B+ we can say A is redundant then reduce to B à C

You will be given a relation (R) with different functional dependency sets X,Y of that relation , you need to check whether one functional dependency is a subset of other (X⊇Y/ Y"⊇"X ) or both are equal (X=Y).   Consider X and Y are two FD sets for a relation R ,   1)If all FDs of X can be determined from FDs that are present in Y , we can conclude that  Y  ⊇   X    or X ⊆ Y    (Y covers X)  .   2)If all FDs of Y can be determined from FDs that are present in X , we can conclude         X ⊇ Y   or Y ⊆ X (X covers Y) . 3) If   1 and 2 are satisfied   then ,we can say   X=Y  or X and Y are equivale nt .

Attribute Closure:   Attribute closure of an attribute set can be defined as set of attributes which can be functionally determined from it . To find attribute closure of an attribute set: Add elements of attribute set to the closure set. Recursively add elements to the closure set which can be functionally determined from the present elements of the closure   set . Attribute closure of an attribute set A of given relation R can be represented as A +

Redundancy in relation may cause insertion, deletion and updation anomalies Normalization  is the process of minimizing  redundancy  from a relation or set of relations . I t helps to minimize the redun dancy in relations , hence avoids anomalies . A functional dependency (FD) for relation R is a formula of the form A à B where A and B are sets of attributes of R. We say A functionally determines the B , or   B   is functionally dependent on the A . Trivial functional dependency :  A → B has trivial functional dependency if B is a subset of A . Non Trivial Functional Dependency : If a functional dependency X->Y holds , where Y is not a subset of X then this dependency is called non trivial Functional dependency . Multi valued   dependency   :   occurs when two attributes in a table are independent of each other but, both depend on a third attribute . Transitive dependency:    functional dependency  is said to b...

A poorly designed database is inconsistent and create issues while adding, deleting or updating information . Poorly designed database stores same data item multiple times , known as Data Redundancy .