1. TOPIC : Programming Model UNIT 1: Modeling Digital Circuits Module 1 : Functional Modeling

2. Programming model All the combinational elements in a circuit can be represented in a programming model. Any logic function is expressed in terms of basic logic operations namely ◦ NOT ◦ AND,NAND ◦ OR,NOR ◦ EXOR,EXNOR Code based programs can be written for any digital circuit using the above operations. Assembly coding is an example of programming model.

3. Example of programming model LDA A//Load A in accumulator XOR B// A xor B STA E// Store A xor B in E XOR C// A xor B xor C STA Sum // store it in Sum LDA E AND C STA F LDA A AND B STA G LDA F OR G STA Cout E G F

4. Register Transfer Language(RTL) Model RTL- A kind of hardware description language (HDL) It is used in describing the registers of a computer or digital electronic system, and the way in which data is transferred between them. In computer, data words are stored in registers and memories are organized as arrays of registers. For example : ◦ register A[0:7] // A is a 8 bit register ◦ memory M[0:7;0:255] // A 256 array of 8 bit register RTLs provide models for systems at the register and instruction set levels.

5. RTL model In this we make HDL models of registered circuits and how signals interact between them such as memories, flip flops, latches, shift registers, and so on. RTL codes are fully synthesizable(can be realized in hardware), because they are written using basic HDL structures. RTL models are characterized as functional, because they emphasize functional description while providing only summary about structural circuits.

6. Example of RTL model E = A XOR B F = E AND Cin G = A AND B S = E XOR Cin Cout = F OR G Here A, B, Cin are input registers and Cout, S are the output registers. E, F, and G are intermediate registers E F G

7. RTL detail Primitive operator : This describes the processing and transfer of data. Example C = A + B Conditional operator : Control of data transformation. For example : if (x) then c = A + B Case operator : This is used for multiway decision. Example : signal{X[0:1]} case 0 : C = A + B; ………. case 3 : C = A – B;