Elation Professional DMX 101 Data, Element, Description, State, Size, Duration, Break, Mtbf, Mtbp

4.3 Data

DMX 512 data is transmitted at 250 kiloHertz (kHz), meaning that 250,000 1’s and 0’s (at a maximum) can be sent each second. Each bit is measured in 4 microsecond (µs) intervals. In order for the receiving device to correctly interpret the data, it must be sent in a particular sequence. A single transmission (DMX Packet) includes synchronizing elements and channel data for up to 512 channels (Figure 8).

				&KDQQHO			&KDQQHO			&KDQQHO
%5($.	0$%	6&	07%)	&'		07%)	&'		07%)		&'	07%3
					'0;3DFNHW

Figure 8

The following table describes each element of the DMX Packet, including its line state, size and duration. An idle DMX line will have a continuous HI (1) line state.

	Table 2: DMX Packet
Element	Description	State	Size	Duration
Break	The Break resets the line,	LO (0)	22-250	88 µs - 1 sec
	signaling a new DMX Packet.		kbits
Mark After	The MAB signals the receiver to	HI (1)	2-250 kbits	8 µs - 1 sec
Break	begin reading data.
(MAB)
Start Code	The SC is identical in size to	Mixed	11 bits	44 µs
(SC)	channel data, but always 0 in
	value.
Mark Time	The MTBF is used to space out	HI (1)	0-250 kbits	Up to 1 sec
Between	individual data bytes.
Frames
(MTBF)
Channel Data	The CD carries the 8-bit DMX	Mixed	11 bits	44 µs
(CD)	Value for each channel, plus one
	start and two stop bits.
Mark Time	The MTBP is used to space out	HI (1)	0-250 kbits	Up to 1 sec
Between	entire DMX Packets.
Packets
(MTBP)

NOTE: At a minimum, a fully loaded DMX Packet (data for all 512 channels) will be around 5700 bits in size. This means about 44 DMX Packets can be sent each second.

WARNING: DMX 512 has no error prevention, and is prohibited from use in life-safety applications such as pyrotechnics or set/rigging motion control.

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