# Control bus

A control bus is (part of) a computer bus, used by CPUs for communicating with other devices within the computer. While the address bus carries the information on which device the CPU is communicating with and the data bus carries the actual data being processed, the control bus carries commands from the CPU and returns status signals from the devices, for example if the data are being read or written to the device the appropriate line (read or write) will be active (logic zero).

## Lines

The number and type of lines in a control bus varies but there are basic lines common to all microprocessors, such as:

• Read ($\overline R$). A single line that when active (logic zero) indicates the device is being read by the CPU. As opposed to a write operation where data goes from the CPU to memory (or an i/o device).
• Perform a hard reboot.
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