Sustem Bus, Fetch Cycle, CPU Flashcards
What are the three system busses
Address buss
Control bus
Data bus
What does the address bus do
Controls where the data is sent from/to
What does the data bus do
Carries data from and to the CPU
What does the control bus do
Carries instruction to be carried out on the fata
What are the 4 address modes
Immediate - data value is in the op code
Register - data is stored in a register
Direct - memory address is in opcode
Indirect - memory address is in a register
What is the opcode
Instruction to be carried out
What is the operand
The data an instruction is to be carried out on
Describe the Fetch in FDE cycle
-Copy address of the instruction pointer into MAR (memory address register)
-Issue read request into the MMU(memory management unit)
- increment instruction pointer
-instruction arrives into MBR(memory buffer register)
Describe decode in FDE cycle
-Place data in MBR (memory buffer register) into Instruction Register
-Decode instruction register
Describe Execute in FDE cycle
- Fetch any operands if needed
- Carry our instruction
- Start next fetch cycle
Name components of CPU
-Control unit
-MMU(MAR and MBR)
- Instruction Pointer
- Current Instruction Register
- Accumulator
- General Purpose registers
- ALU (arithmetic logic unit)
What is the Bit Length
The number of bits that can be transferred in one operation
