Control bus - Wikipedia Control bus This article is about a kind of bus used inside one box. For a kind of bus that connects several boxes in a networked control system, see Fieldbus. In computer architecture, A control bus is part of the system bus, used by CPUs for communicating with other devices within the computer. While the address bus carries the information about the device with which the CPU is communicating 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 is being read or written to the device the appropriate line ( read or write ) will be active ( logic one ). Contents 1 Lines 2 See also 3 References 4 External links Lines The number and type of lines in a control bus varies but there are basic lines common to all microprocessors, such as : Read ( R D  ̄ ( displaystyle ( overline ( RD ) ) ) ). A single line that when active ( logic zero ) indicates the device is being read by the CPU. Write ( W R  ̄ ( displaystyle ( overline ( WR ) ) ) ). A single line that when active ( logic zero ) indicates the device is being written by the CPU. Byte enable ( E  ̄ ( displaystyle ( overline ( E ) ) ) ). A group of lines that indicate the size of the data ( 8, 16, 32, 64 bytes ). The RD and WR signals of the control bus control the reading or writing of RAM, avoiding bus contention on the data bus. Additional lines are microprocessor - dependent, such as : Transfer ACK ( `` acknowledgement '' ). Delivers information that the data was acknowledged ( read ) by the device. Bus request. Indicates a device is requesting the use of the ( data ) bus. Bus grant. Indicates the CPU has granted access to the bus. Interrupt request. A device with lower priority is requesting access to the CPU. Clock signals. The signal on this line is used to synchronize data between the CPU and a device. Reset. If this line is active, the CPU will perform a hard reboot. Systems that have more than one bus master have additional control bus signals that control which bus master drives the address bus, avoiding bus contention on the address bus. See also Address bus Cache bus Data bus Bus mastering References ^ Jump up to : Ian Sinclair ; John Dunton. `` Practical Electronics Handbook ''. 2013. section `` The control bus ''. p. 209 - 210. External links Definition by Webopedia. Computer system organization at the University of California, Riverside. `` Hardware and Software Architecture '', a PowerPoint presentation at California State University, Los Angeles. Technical and de facto standards for wired computer buses General System bus Front - side bus Back - side bus Daisy chain Control bus Address bus Bus contention Network on a chip Plug and play List of bus bandwidths Standards SS - 50 bus S - 100 bus Multibus Unibus VAXBI MBus STD Bus SMBus Q - Bus Europe Card Bus ISA STEbus Zorro II Zorro III CAMAC FASTBUS LPC HP Precision Bus EISA VME VXI VXS NuBus TURBOchannel MCA SBus VLB PCI PXI HP GSC bus InfiniBand UPA PCI Extended ( PCI - X ) AGP PCI Express ( PCIe ) Direct Media Interface ( DMI ) RapidIO Intel QuickPath Interconnect NVLink HyperTransport Infinity Fabric Intel UltraPath Interconnect Storage ST - 506 ESDI IPI SMD Parallel ATA ( PATA ) SSA DSSI HIPPI Serial ATA ( SATA ) SCSI Parallel SAS Fibre Channel SATAe PCI Express ( via AHCI or NVMe logical device interface ) Peripheral Apple Desktop Bus DCB HP - IL HIL MIDI RS - 232 RS - 422 RS - 423 RS - 485 DMX512 - A IEEE - 488 ( GPIB ) IEEE - 1284 ( parallel port ) UNI / O ACCESS. bus 1 - Wire D2B I2C SPI Parallel SCSI Profibus IEEE 1394 ( FireWire ) USB Camera Link External PCIe Thunderbolt Audio ADAT Lightpipe AES3 Intel HD Audio I2S MADI McASP S / PDIF TOSLINK Portable PC Card ExpressCard Embedded Multidrop bus CoreConnect AMBA Wishbone SLIMbus Interfaces are listed by their speed in the ( roughly ) ascending order, so the interface at the end of each section should be the fastest. This computer hardware article is a stub. You can help Wikipedia by expanding it. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Control_bus&oldid=795194634 '' Categories : Computer buses Computer hardware stubs Talk Read Contents About Wikipedia Čeština Español Français Bahasa Indonesia Nederlands Polski Русский සිංහල Српски / srpski Українська 中文 Edit links This page was last edited on 12 August 2017, at 17 : 15. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: what are the main functions of the control bus
Answer: communicating with other devices within the computer