dmx_basics:dmx_timing
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dmx_basics:dmx_timing [2012/01/06 06:15] – created Jan_K | dmx_basics:dmx_timing [2013/03/11 03:45] (current) – external edit 127.0.0.1 | ||
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DMX512 sends packages of up to 512 frames with 8 bit data to fixtures.\\ | DMX512 sends packages of up to 512 frames with 8 bit data to fixtures.\\ | ||
Normally only the used addresses are send which means if only up to address 10 are used, only 10 frames are send.\\ | Normally only the used addresses are send which means if only up to address 10 are used, only 10 frames are send.\\ | ||
- | The max number of frame that can be send is 512.\\ | + | The max number of frame that can be send is 512. (Start frame + 511)\\ |
- | The packet don’t contain | + | Start Frame or Address 0 is a sync frame that can't be addressed on the fixtures.\\ |
+ | The packet don’t contain | ||
To synchronize all receivers to the transmitter, | To synchronize all receivers to the transmitter, | ||
Each receiver will from this “MAB” point, count frames and wait for the ones addressed to them.\\ | Each receiver will from this “MAB” point, count frames and wait for the ones addressed to them.\\ | ||
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The data are clocked out with 250 KHz and his gives a bit time of 4uS.\\ | The data are clocked out with 250 KHz and his gives a bit time of 4uS.\\ | ||
+ | {{: | ||
+ | \\ | ||
+ | Starting from the end of the last packets stop bits the state will be idle mode. \\ | ||
+ | Idle mode or MARK TIME BETWEEN PACKETS ,”MTBP” is the time between the packages where the signal is high. This time can be from 0 to 1 sec.\\ | ||
+ | \\ | ||
+ | Then a Break is send as a start on the packet.\\ | ||
+ | The Break are minimum 2 frames long. Corresponding to 22 bits.\\ | ||
+ | \\ | ||
+ | And then comes a MARK AFTER BREAK, “MAB” which are 2 bit long.\\ | ||
+ | \\ | ||
+ | Then the frames comes one by one and the first frame (frame 0) is a start code that tells what is in this packet.\\ | ||
+ | If it is a normal fixture control packet then it will be 0x00 as start code and in the next frames will be a control value from 0 to 255.\\ | ||
+ | \\ | ||
+ | **Frame.**\\ | ||
+ | The frame consists of a start bit which is always low. This makes the a high low transition to indicate the start of the frame.\\ | ||
+ | Then 8 bits are send.\\ | ||
+ | And finally are 2 stop bits, that are high, send.\\ | ||
+ | This gives a total of 11 bits per frame.\\ | ||
+ | The frame can be hold high after the stop bit. This time is the MARK TIME BETWEEN FRAME, “MTBF”. This time can be from 0 to 1 sec.\\ | ||
+ | When the last Frame has been send the transmitter goes into high, Idle state again.\\ | ||
+ | |||
+ | {{: | ||
+ | \\ | ||
+ | nd = not defined.\\ | ||
+ | \\ | ||
+ | A full packet containing 512 frames (Start Frame + 511) will then be 22, mS\\ | ||
+ | \\ | ||
+ | Break + MAB + (Start Frame + MTBF) + 511*(Frames + MTBF) + MTBP idle\\ | ||
+ | \\ | ||
+ | The shortest full pack will then be\\ | ||
+ | 88 + 8 + (44 + 0) + 511*(44 + 0) + 0 = 22624 uS or 22,624 mS.\\ | ||
+ | \\ | ||
+ | This is running with the absolute min values and MTBF and MTBP Idle set to 0.\\ | ||
+ | \\ | ||
+ | However times like Break and MTBP can with good sense be prolonged and at the end give a more stable system. \\ | ||
+ | MTBP Idle is normally used to adjust the refresh rate.\\ | ||
+ | \\ | ||
+ | \\ | ||
+ | **Note:**\\ | ||
+ | Sometimes words like DMX 1024 and DMX 128 pops up.\\ | ||
+ | DMX 1024 means that there are 2 universes, DMX512, running in parallel.\\ | ||
+ | DMX 128 means that only up to 128 channel are send. (Start Frame + 127)\\ | ||
+ | On the fixture side this means nothing they all run DMX512 and in the DMX1024 system there will be 2 physical connection available each running DMX512.\\ | ||
+ | The DMX128 means that in practice only addresses up to 127 can be used because address 0 is the start sync and it is not a legal address on the fixture.\\ | ||
+ | \\ | ||
+ | \\ | ||
---- | ---- | ||
+ | \\ |
dmx_basics/dmx_timing.1325830554.txt.gz · Last modified: 2013/03/11 02:57 (external edit)