Question

How are address, data and control signals connected to the various components within the computer system?

Answer 1

SOLUTION:- System bus is the internal communication channel connecting all hardware devices. The system bus connects the CPU with main memory and other system components (i.e., storage and I/O devices and other peripheral devices) Any bus is a shared electrical or optical channel that connects two or more devices.

We can divide the components of a system bus into specialized subsets, comprising the data bus, the address bus and the control bus.

The Address Bus:- The address bus performs the transmission of a memory address if the primary storage is the sending or receiving device. The address bus contains 16,24 or 32 parallel signal lines. The number of lines decides the memory amount that will be directly addressed as each line carries 1 bit of the address. If the CPU contains N address lines, then it will directly address 2^N address lines. For e.g., a computer with 32 bit address can address 4 GB of physical memory. CPU reads/writes data from the memory by addressing a unique location and outputs the location of the data on the address bus then memory uses this address to access the proper data. Each I/O device has a unique address. When accessing a I/O device, CPU places its address on the address bus, Each device will detect if it is its own address and perform accordingly.

The Data Bus:- The data bus performs the transmission of data between computer system components. The data bus is a bidirectional route, that works as a carrier for the real data between the processor, the memory and the peripherals. The data bus contains 8,16,32 or 64 parallel signal lines because each wire can transfer 1 bit of data at a time, an 8 wire bus can transfer 8 bits at a time(i.e., a full byte). When the CPU fetches data from memory, it firstly outputs the address on the address bus then the memory outputs the data onto the data bus then the CPU reads the data from data bus. When writing data onto the memory, the CPU outputs firstly the address on the address bus then outputs the data onto the output bus then memory reads and stores the data at the proper location.

The Control Bus:- The control bus works as a carrier for commands, command responses, status codes, and similar messages. It also carries the control, timing and coordination signals to manage the various functions across the system. The Computer system components synchronizes their tasks via sending signals over the control bus. These control signals indicates whether the data is to be read into or written out the CPU, whether the CPU is accessing memory or an I/O device, and whether the I/O device/memory is ready for the data transfer. For e.g., 1 line of the bus will be utilized to indicate whether the CPU is currently reading from or writing to main memory. Others will be considered as I/O Read/Write.

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