1. Lec. 10 Assembly Programming Dr. Tamer Samy Gaafar Microprocessors

2. Quiz Draw a flow chart for converting an octal number to binary. Write the required program assuming the octal number is 356 where address 56 …………. Contains 3 address 57 …………. Contains 5 address 58 …………. Contains 6 Store the result at address 59.

3. The 6800 Microprocessor

4. 6800 Microprocessor It was first released by Motorola in the mid 1970’s. Today, it is being second sourced by several other companies. 6808 is another version of this proc. The primary difference between 6800 & 6808 is the means by which clock signals are generated. The 6808 has an on-chip clock circuit.

5. 6800 Microprocessor

6. Architecture of 6800 Microprocessor Computer Architecture : is used to describe the construction of computer i.e. Register Size and arrangement. Bus Configuration

8. The Programming Model

9. The Programming Model of 6800 MPU

10. Two Accumulators Accumulator A (ACCA) Accumulator B (ACCB)

11. Program Counter PC …………… 16 bits. Address is 16 bits …… 65536 address. How can we specify a 16 bit address with an 8-bit address bus? Extended addressing mode ….two bytes are used to represent each address.

12. Condition Code Register

13. Index Register 16 bit general purpose register. It allows a powerful addressing mode called indexed addressing. It holds 2 byte instead of one byte.

14. Block Diagram of the 6800 MPU

15. Note Address bus is 16 bit. Address registers are 16 bits. Any of the 16 bit registers can be loaded from data bus which is only 8 bits. So 2 operations are required. Upper half of the affected register is loaded first then the lower half.

16. Instruction Set of The 6800 MPU

17. Types of Instructions Arithmetic Data Handling. Logic. Data Test. Index Register. Stack Pointer. Jump, Branch & Condition Code.

18. Arithmetic Instructions

19. means condition code is un affected. means test and set if true, clear otherwise.

20. Data Handling Instructions

22. Rotate Left

23. Rotate Right

24. Arithmetic Shift Left

25. Arithmetic Shift Right

26. Logical Shift Right

27. TAB & TBA Instruction TAB Copies contents of accumulator A into accumulator B. TBA Copies contents of accumulator A into accumulator B.

28. Logical Instructions

30. Data Test Instructions

32. The End