E3165 DIGITAL ELECTRONIC SYSTEM
This comprehensive guide covers the essentials of programming within digital electronic systems, focusing on the composition of instructions, the structure of programming, and addressing modes. It explains key concepts such as effective addressing (EA), various addressing modes in the MC68000 architecture, and programming constructs such as loops and subroutines. The document outlines the steps involved in program building, including problem definition, logical design, documentation, and testing. Understanding these elements is crucial for efficient program implementation and optimization in microprocessor environments.
E3165 DIGITAL ELECTRONIC SYSTEM
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Presentation Transcript
INTRODUCTION • Programming – process of composing several instructions to perform certain tasks. • Program – product of programming which contains several instructions. • Skills of programming / structure of programming implementation: • Essential and best instructions to perform a certain task. • How instructions organized in subprogram (subroutine) so it can be reused as many times as possible. • Used minimum lines of instructions for maximum tasks. • Addressing modes – procedure of fetching and sending data between source and destination.
ADDRESSING MODES • MC68000 : 14 different addressing modes divided into 6 groups. • By understanding the addressing modes, we have EA (effective address). • EA will help us identifies the location of an operand.
REGISTER DIRECT ADDRESSING • Dn – Data register direct addressing. (D1,D2,D3,D4,D5,D6,D7) • An – Address register direct addressing. (A1,A2,A3,A4,A5,A6,A7) • Fastest and most compact because no reference to memory.
ABSOLUTE DATA ADDRESING • EA in memory. Ex : MOVE.L $1234,D4 • Absolute short data: • 16 bits address. • 000000 – 007FFF FF8000 - FFFFFF • Absolute long data: • 24 bits address. • 000000 – FFFFFF
PROGRAM COUNTER RELATIVE / RELATIVE • Program counter relative with offset • EA = offset + value in PC = d16 + PC d16 will be sign-extends to 32 bits first. 00122002
PROGRAM COUNTER RELATIVE / RELATIVE • Program counter relative with index and offset • EA = index + offset + value in PC = Xn + d8 + value in PC Xn – data or address register d8 will be sign-extends to 32 bits first. 00010202
REGISTER INDIRECT ADDRESSING • Address register indirectly referred. • 5 modes: • Address register indirect. • Postincrement address register indirect. • Predecrement address register indirect. • Address register indirect with offset. • Address register indirect with index and offset.
CONCEPT OF PROGRAMMING • Steps in program building: • Definition of problem. • Logical design. • Programming. • Documentation of the program. • Analysis the program. • Test run the program.
EXAMPLE • Definition of problem: • Input data of two numbers. These two numbers are added. The product is stored in a memory location. • Logical design – flow chart Programming model of the microprocessor (Figure 2.15 : Unit 2/38)
EXAMPLE (cont.) • Programming.
EXAMPLE (cont.) • Documentation of program.
EXAMPLE (cont.) • Analysis the program
EXAMPLE (cont.) • Analysis the program
EXAMPLE (cont.) • Analysis the program • Test run the program • ASM68K – assembler • SIM68K - simulator
IMPLEMENTATION STRUCTURE OF PROGRAMMING • Effective programming is the know how to identify the best or optimum tools. (composition of instructions and selection of addressing modes) • Good program is with the features of least instruction lines, least executions duration, easy alteration and modifications. • Structure of programming: • Construct of sequential • Construct of loop • Construct of decision making by branch/jump • Construct of subroutine
Instruction-1 Instruction-1 Instruction-n START END CONSTRUCT OF SEQUENTIAL • Basic, simple and straight forward. • Execute one instruction after another.
Instruction-1 LOOP Instructions : JUMP LOOP START Instruction-2 Instruction-n LOOP (b) Instructions (a) Flow chart CONSTRUCT OF LOOP • Some instruction need to be repeated – loop construct. • At the end of the program, assert an instruction to instruct the program execution to go back to the first instruction.
CONSTRUCT OF DECISION MAKING BY BRANCH/LOOP • Another structure of loop construct where the program is allowed to decide whether to implement the loop or not.
CONSTRUCT OF SUBROUTINE • To simplify a very long or complex program. • Grouping several instructions that tend to be repeated. This subroutine need to be name for easy call.
