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Lecture 4 assembly language
The document provides an overview of assembly language, including: - Assembly language is a symbolic representation of machine language that facilitates program writing. An assembler translates assembly code into machine code. - Assembly language is hardware dependent and differs for each processor type. It offers advantages like debugging, compilers, embedded systems, and optimized code size/speed. Disadvantages include development time, reliability, maintainability, and portability. - Assembly language elements include labels, mnemonics, operands, and comments. Macros and subroutines can simplify programs by grouping instructions as single entities.
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Lecture 4 assembly language
- 1. ASSEMBLY LANGUAGE T SPradeep Kumar VIT University – Chennai Campus http://www.pradeepkumar.org
- 2. Topics • CPU Behavior •Accumulator Based CPU • Assembly language • Pros and Cons of Assembly Language • Elements of Assembly Language • Example: AC = AC x N • Greatest Common Divisor • Macros and Subroutines
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- 5. Accumulator based CPU •All the arithmetic calculations happens at the Accumulator register • Instructions are fetched by the program control Unit (PCU). • They are executed in Data processing Unit (DPU) • Instruction are typically look like this • X1 = fi (X1, X2) • X1, X2 denotes a CPU register (AC, DR, or PC) or an external memory location M (address)
- 6. Accumulator based CPU •fi is operation performed by the ALU are limited to Fixed point addition, subtraction, shifting and logical operations.
- 7. Assembly Language • Anassembly language is a symbolic representation of the machine language of a specific processor, augmented by additional types of statements that facilitate program writing and that provide instructions to the assembler • An assembler is a program that translates assembly language into machine code. • Assembly Language is hardware dependent with a different assembly language for each type of processor.
- 8. Advantages of AssemblyLanguage over HLL • Debugging and Verification • Making compilers • Embedded systems • Hardware drivers and system code • Accessing instructions that are not accessible from HLL • Self modifying code • Optimizing code for size and speed • Function libraries
- 9. Disadvantages of Assemblylanguage • Development time • Reliability and security • Debugging and verifying is difficult • Maintainability • Portability • Compilers have been improved a lot in recent years
- 10. Assembly language elements •Label • Mnemonic • Operands • Comment
- 11. Example: AC =AC x N Label Mnemonic, operands Comments One 00…001 The constant one Multi N The multiplier Ac 00...000 Location for initial value of Y in AC Prod 00…000 Location for partial product P ST ac Save initial value of Y of AC Loop LD mult Load N into AC to test for termination BZ exit Exit if N=0; otherwise continue LD one Load 1 into AC MOV DR, AC Move 1 from AC to DR LD mult Load N into AC to decrement it SUB Subtract 1 from N ST mult Store decremented N LD ac Load initial value Y of AC MOV DR, AC Move Y from AC to DR
- 12. Continued… Label Mnemonic, operands comments LD prod Load current partial product P ADD Add Y to P ST prod Store the new partial product P BR loop Branch to Loop Exit …..
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- 15. Macros and Subroutines •Macros and subroutines are useful for the simplification of program • Group of instructions to be treated as a single entities • Name MACRO Operand,… ………} ENDM • Macros are helpful in creating new opcode names • Introduce new data types and addressing modes
- 16. Macros • Example ofMACRO • LDAI MACRO ADR LDHL ADR MOV A,M ENDM Later, LDAI 1000H becomes a separate instruction
- 17. Subroutines • Also calledas procedure • A subroutine definition is assembled into object code • Two executable instructions • CALL or JUMP TO SUBROUTINE • RETURN CALL SUB1 NEXT ….. …... SUB1 …… …… RETURN
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