System Bus Design
Definition:
The electrically conducting path along which data is transmitted inside any digital electronic device. A Computer bus consists of a set of parallel conductors, which may be conventional wires, copper tracks on a PRINTED CIRCUIT BOARD, or microscopic aluminum trails on the surface of a silicon chip. Each wire carries just one bit, so the number of wires determines the largest data WORD the bus can transmit: a bus with eight wires can carry only 8- bit data words, and hence defines the device as an 8-bit device.
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- The bus is a communication channel.
- The characteristic of the bus is shared transmission media.
- The limitation of a bus is only one transmission at a time.
- A bus which is used to provide communication between the major components of a computer is called a System bus.
Computer:
System bus contains 3 categories of lines used to provide the communication between the CPU, memory and IO named as:
1. Address lines (AL) 2. Data lines (DL) 3. Control lines (CL)
1. Address Lines:
- Used to carry the address to memory and IO.
- Unidirectional.
- Based on width of a address bus we can determine the capacity of a main memory
Example:
2. Data Lines:
- Used to carry the binary data between the CPU, memory and IO.
- Bidirectional.
- Based on the width of a data bus we can determine the word length of a CPU.
- Based on the word length we can determine the performance of a CPU.
Example:
3. Control Lines:
- Used to carry the control signals and timing signals
- Control signals indicates type of operation.
- Timing Signals used to synchronize the memory and IO operations with a CPU clock.
