DMX512(1990)Protocol.pdf
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1、 United States Institute for Theatre Technology, Inc. = U S I T T = DMX512/1990 DIGITAL DATA TRANSMISSION STANDARD FOR DIMMERS AND CONTROLLERS _ APRIL 1990 A Revision of the DMX512 Standard Published in August1986 A Project of the USITT Engineering Commission U S I T T 10 W. 19th St. - Suite 5A New
2、York, NY 10011-4206 (212) 924-9088 (212) 924-9343 FAX DMX512/1990 Digital Data Transmission1.0 SCOPEThis Standard describes a method of digital data transmission betweencontrollersand dimmers. It covers electrical characteristics, data format, dataprotocol,connector type, and cable type.2.0 APPLICAB
3、ILITYThis Standard is intended as a guide for:1. Equipment manufacturers and system specifiers who wish tointegrate systems of dimmers and controllers made by different manufacturers.2. Equipment manufacturers seeking to adopt a standard controller-dimmer digital transmission protocol.Although wides
4、pread adoption of this standard is sought by USITT,compliance withthe standard is strictly voluntary. Furthermore, it is not intendedas areplacement for existing protocols already manufactured, but ratheras an additionto existing protocols which will broaden the installed base ofcontrollers anddimme
5、rs that can communicate with each other.3.0 CROSS REFERENCESee EIA standards EIA-422A and EIA-485 available from: Electronic Industries Association Standards Sales Office 2001 Eye Street NW Washington, D.C. 2006 202-457-49004.0 ELECTRICAL SPECIFICATIONSThis standard shall follow EIA Standard EIA-485
6、 (an enhanced versionof EIA-422A)with regard to all electrical characteristics including line driverand receiverselection, line loading, and multi-drop configurations.4.1 COMMON MODE VOLTAGESEquipment designers are advised to pay particular attention to theCommon Modevoltage provisions of EIA-485 in
7、 the choice of transmitter andreceiver componentsand general system implementation.4.2 ELECTRICAL ISOLATIONThis standard and EIA-485 make no general provisions for electricalisolation.However, suitable optical isolation, transformer isolation, or othermeans may beemployed to prevent the undesirable
8、propagation of voltages whichexceed the CommonMode limits of EIA-485. The inclusion of such isolation does not,however, alterthe requirement that a transmitter or receiver conform to EIA-485. DMX512/1990 - 1 - April19905.0 DATA PROTOCOLData transmitted shall be in asynchronous serial format. Dimmerl
9、evel data shall betransmitted sequentially, beginning with dimmer 1 and ending with thelastimplemented dimmer, up to a maximum of 512. Prior to the first leveltransmitted, aRESET signal shall be transmitted followed by a NULL START code.Valid dimmerlevels shall be 0 to 255 decimal (00 to FF hexadeci
10、mal) representingdimmer controlinput levels of OFF to FULL in a linear relationship. These numericvalues shallnot necessarily have any relationship to actual dimmer output, whichshall bedetermined within the dimmer itself.5.0.1 RESET SIGNALThe RESET signal (Timing Diagram, Designation #1) shall cons
11、ist of aBREAK lasting88 uSeconds (two frame times) or any longer duration. A BREAK shallbe defined as ahigh-to-low transition followed by a low of at least 88 uSeconds.All dimmers andother receiving devices shall interpret any such BREAK as aterminator for anypending transmission/data packet and its
12、 end as the start of the MARKAFTER BREAKand START code sequence at the beginning of the next packet.5.0.1.1 MARK AFTER BREAKThe duration of the MARK seperating the RESET/BREAK and the STARTcode (TimingDiagram, Designation #2) shall be not less than 8 uSeconds and notgreater than 1Second. All DMX512/
13、1990 transmitters shall produce a MARK AFTERBREAK of not lessthan 8 uSeconds. All receivers shall recognize an 8 uSecond MARKAFTER BREAK.Receivers capable of also recognizing the shorter 4 uSecond MARKAFTER BREAK (asspecified in the 1986 DMX512 Standard) may be identified and markedas having thiscap
14、ability as per paragraph 11.05.0.2 NULL START CODEThe NULL START code shall be defined as a properly framed NULLcharacter (all zeros)following a RESET. The NULL START identifies subsequent data assequential 8-bitdimmer level information.5.0.3 OTHER OPTIONAL START CODESIn order to provide for future
15、expansion and flexibility, thisStandard makesprovision for 255 additional START codes (1 through 255 decimal, 01through FFhexadecimal). For this reason, a dimmer receiver must not accept as8-bit leveldata any data packet with a START code other than NULL STARTfollowing the RESET.5.0.4 MAXIMUM NUMBER
16、 OF DIMMERSEach data link shall support up to 512 dimmers. Multiple links shallbe used wherelarger numbers of dimmers are required. DMX512/1990 - 2 - April19905.0.5 MINIMUM NUMBER OF DIMMERSThere shall be no minimum number of dimmers on the data link. DMX512data packetswith levels for less than 512
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