E3165 DIGITAL ELECTRONIC SYSTEM

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 registerd8 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.

ADDRESS REGISTER INDIRECT

POSTINCREMENT ADDRESS REGISTER INDIRECT

PREDECREMENT ADDRESS REGISTER INDIRECT

ADDRESS REGISTER INDIRECT WITH OFFSET

ADDRESS REGISTER INDIRECT WITH INDEX AND OFFSET

IMMEDIATE DATA ADDRESSING

INCORRECT INSTRUCTIONS

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

CONSTRUCT OF SEQUENTIAL• Basic, simple and straight forward.• Execute one instruction after another.

START

Instruction-1

END

Instruction-1

Instruction-n

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.

Instruction-1

(a) Flow chart

Instruction-2

Instruction-n

START

LOOP

Instructions

:

JUMP LOOP LOOP

(b) Instructions

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.

CONSTRUCT OF SUBROUTINE