2. Content
Language Levels
High Level micro code
Machinecode language
Assembler languages
Structure
Commands
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3. Language Levels
High Level Language
Assembler Language
Machine Language Normally deepest free
accessible Level
Micro „Firmware“
-programming
Hardware
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4. High Level Micro Code
High Level language
Formulating program for certain application
areas
Hardware independent
Assembler languages
Machine oriented language
Programs orient on special hardware
properties
More comfortable than machine code
(e.g. by using symbolic notations)
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5. High Level Micro Code
Machine code:
Set of commands directly executable
via CPU
Commands in numeric code
Lowest semantic level
Generally 2 executing oportunities:
• Interpretiv via micro code
• Directly processing via hardware
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6. High Level Micro Code
Micro programming:
Implementing of executing of machine
commands (Control unit - controller)
Machine command executed/shown
as sequence of micro code
commands
Micro code commands:
• Simpliest process controlling
• Moving of data
• Opening of grids
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• Tests
7. Machinecode language
Machinecode command:
Binary word (fix length, causes
elementary operations within CPU)
Machinecode program
sequence of machinecode commands
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8. Machinecode language
Structure: OpCode OpAddress
Operationcode
• Defining executable operation
Operandaddress
• Spezification of operands
• Constants/register addresses/storage
addresses
Difference between 1/2/3 address
machines
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9. Machinecode language
Data transport commands
Arithmetic and logical commands
Process controlling commands
In-/output commands
Special commands
Disadvantage:
Difficultly readable
No symbolic names(Mnemomics)
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10. Assembler languages
Translated into machinecode
language(Interpreter)
Each operation code(opcode) owns one
symbolic command
Assignments of operand addresses are
possible
Labels for command addresses
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11. Assembler languages
Usage of pseudo commands
Commands for assembler
Assigment of values/addresses(variables)
Definition of the programstart addresses
Allocating of memory for variables
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12. Assembler languages-structure
<Label> <Mnemomic> <Operand> Comments
Label
symbolic labeling of an assembler address
(command address at Machine level)
Mnemomic
Symbolic description of an operation
Operands
Contains of variables or addresse if necessary
Comments
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13. Assembler Languages
- Machine Instructions
Bitpatterns are created, executed as
commands by CPU
Classes:
Arithmetic/logical Operations(ADD,SUB,XOR,
administrative commands - EQU,
shifting&rotation commands)
Data transfer(load/save operations,
speicher<>register, register<>register)
Control commands(jump op. [un-]conditional
/relativ,control op. – STOP)
In-/output commands
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14. Assembler – Assembler Instructiuons
(Pseudo Commands)
Instructions to assembler
Controlling translation process
No creation of machine code
Affect creation of machine instructions
Types:
Program organisation
equations and symbolic Addresses
Definition of Constants and Memory
Addressing
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15. Assembler – All purpose Register
Arithmetic example:
Source and Destination Data width has to
euqal
AX , BX, CX, DX, SI, DI, BP, SP
; arithmetic operations
All purpose
ADD AX, BX ; AX := AX+BX Register
SUB AH,AL ; AH := AH - AL
MOV AL, CL ; AL := CL AX AH AL
INC CX ; CX := CX+1
DEC CL ; CL := CL-1 BX BH BL
NEG CX ; CX := -CX
CX CH CL
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16. Assembler – Special Register
Unless to all-purpose registers
Special register(SS, DS, CS, ES, IP)
• Never ever are
• Destination/Source of a „mov“ command
• Destination of arithmetic operations
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17. Assembler – Flag Register
O D I T S Z A P C
Zero
Sign Carry
Trap Parity
Interrupt enable Auxiliary carry
Direction
Overflow
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18. Assembler – Flag Register
FLAG-Bits:
C Carry Area crossing of unsigned numbers
A Aux. Carry Area crossing at BCD-design
O Overflow Area crossing at arithmetic
operation with signed numbers
S Sign True if result = negativ
Z Zero Result = Null
P Parity Result has an even number of 1 Bits
D Direction flag Defines direction of string-
commands
I Interrupt Global Interrupt Enable/Disable Flag
T Trap Flag Used by debugger, allows single-step-
modus
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19. Assembler – Flag Register
Missing flags:
• V: Two’s complement overflow indicator
• H: Half Carry Flag
Operations and flags
ADD, SUB, NEG affects O, S, Z, A, P, C
INC, DEC -“- O, S, Z, A, P
MUL, DIV -“- O, C
AND, OR , XOR -“- S, Z, P, C
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