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. ▫ – 007FFF FF FFFFFF Absolute long data: ▫24 bits address. ▫ – 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

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

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