Please enable JavaScript.
Coggle requires JavaScript to display documents.
Instruction Set - Coggle Diagram
Instruction Set
x86 Data Types
8 bit Byte
16 bit word
32 bit double word
64 bit quad word
128 bit double quadword
Addressing is by 8 bit unit
Words do not need to align at even numbered address
Data accessed across 32 bit bus in units of double word read at addresses divisible by 4
Little endian
Elements of Instruction Set
Operation code
Specifies the operation to be performed (e.g., ADD, I/O). The operation is specified by a binary code, known as the operation code, or opcode
Source operand reference
The operation may involve one or more source
operands, that is, operands that are inputs for the operation
Result operand reference
The operation may produce a resul
Next instruction reference
This tells the processor where to fetch the next instruction after the execution of this instruction is complete
Source and result operands can be in one of four areas
Main or virtual memory
As with next instruction references, the main or virtual memory address must be supplied
Processor register
With rare exceptions, a processor contains one or more registers that may be referenced by machine instructions. If only one register exists,reference to it may be implicit. If more than one register exists, then each register is assigned a unique name or number, and the instruction must contain the number of the desired registe
immediate
The value of the operand is contained in a field in the instruction being executed
I/O device
The instruction must specify the I/O module and device for the operation. If memory-mapped I/O is used, this is just another main or virtual
memory address
Instruction Types
Data processing
Addition, subtraction, multiply, AND, OR, etc
Data storage (main memory)
Store something to memory
Data movement (I/O)
Display something to monitor
Program flow control
If a<5 then ...
Types of Operand
Addresses
Numbers
Signed/Unsigned
Integer/floating point
Characters
ASCII etc
Logical Data
Bits or flag
Instruction Representation
Within the computer, each instruction is represented by a sequence of bits. The instruction is divided into fields, corresponding to the constituent elements of the instruction
Opcodes are represented by abbreviations, called mnemonics, that indicate the
operation
ADD Add
SUB Subtract
MUL Multiply
DIV Divide
LOAD Load data from memory
STOR Store data to memory
Operands are also represented symbolically. For example, the instruction
ADD R, Y
may mean add the value contained in data location Y to the contents of register R. In this example, Y refers to the address of a location in memory, and R refers to a particular register
The complete collection of instructions
that are understood by a CPU