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Programming 68HC11

Programming 68HC11. Steps in programming MPU. START. FETCH TO CODE. DECODE OP CODE. FETCH OPERAND ADDRESS IF ANY. EXECUTE THE INSTRUCTION. Programming Language machine. $ indicate that the address is in hex LDAA load accumulator A B6 STAA store accumulator A B7

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Programming 68HC11

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  1. Programming 68HC11

  2. Steps in programming MPU START FETCH TO CODE DECODE OP CODE FETCH OPERAND ADDRESS IF ANY EXECUTE THE INSTRUCTION

  3. Programming Language machine

  4. $ indicate that the address is in hex • LDAA load accumulator A B6 • STAA store accumulator A B7 • ADDA add to accumulator A BB • SUBA subtract to accumulator A B0 • WAI halt 3E • JMP jump 7E • BEQ branch if equal to zero 27

  5. Jump branch instruction

  6. Branch Equal to Zero (BEQ) instruction

  7. Terms • Offset determines MPU’s next instruction • C1, 00 address of operand X • C1, 01 address of operand Y • C1, 02 address where the contents of the accumulator A will be stored • C1, 5F address of next instruction • C3, 00 address of location where the contents of A will be stored

  8. Assembly language source program

  9. LDAA code Object Code Source Code B6 D0 FF $D0FF LDAA

  10. Assembly process typical steps • The online assembler program is loaded into the computer’s internal RAM’s (unless it is already in ROM) • The programmer loads the assembly language source program into the computer’s RAM, either from the keyboard or an external memory unit (like when using ASCII code for the characters)

  11. Continuation • The computer then is commanded to execute the one-line assembler program • The computer executes the one-line assembler program which converts source code instruction such as LDAA $D0FF into object code that I places into RAM • Once instruction is placed in RAM the program then can be stored in disk for later use

  12. Continuation • The object program can now be executed since it is in the executable machine.

  13. High level languages • BASIC • FORTRAN • TURBO C++

  14. Flowchart Start Initialize COUNT=7 Initialize RESULT=0 Read data byte from sensor Add to RESULT Decrement COUNT Is count =0 ? no yes Store result in memory stop

  15. Problems • How many consecutive location does an 8 bit microcomputer store a 48 bit word? • Answer • 48 bit / 8 bit • 6 consecutive memory location

  16. A certain 32 bit computer has the following instruction word format: • How many different instructions can this instruction word specify? • How many different memory addresses can it specify? • What internal memory capacity would this computer • require to operate at full capacity? Answer a) 256 bits b) 65536 c) 65536

  17. During the LDAA instruction data are taken from__________ and transferred to ___________ Memory location STAA

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