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DMX Interface

The UART DMX/RDM interface of the Pluggy module consist of 3 digital signals that can be used to interface an RS485 driver IC compliant with the ANSI E1.11 DMX512-A standard to facilitate a DMX512-A compatible interface. Please refer to the example schematic for details on how to connect an RS485 driver IC. DE and DI signals shall both be connected to the direction pin (RS485_DIR).

The DMX interface can also be used for CMOS/TTL level directly interfacing, for instance to a host CPU.

NOTE: Signal on RXD pin must NOT exceed 3.3V ! If 5V signal is used, a level shifting circuit must be used - for instance a voltage divider.

DMX and RDM termination and line bias

DMX and RDM termination and line bias circuitry is not provided as part of Pluggy (since the data is provided at TTL level). This circuit is left to the device manufacturer to provide as required for each particular application and device.

Termination and line bias circuitry requirements shall follow ”ANSI E1.20 - 2006 / Entertainment Technology-RDM-Remote Device Management over USITT DMX512 Networks” or later revisions.

IMPORTANT: Biasing is mandatory for all RDM implementations.

DMX frame rate and size

Pluggy will auto sense the DMX frame rate and frame size and accept all variations that are within the USITT DMX-512 (1986 & 1990) and DMX-512-A standards.

Minimum DMX frame size is 1 slot and maximum is 512 slots.

Minimum DMX frame rate for normal operation is 0.8 frames per second and maximum is 830 frames per second.

Input frame rates below 0.8 frames per second, i.e. more than 1.25s has elapsed since the start of the last frame, will be treated as a loss of DMX. Pluggy modules in receiver mode will set the RS485 driver IC to input mode until another DMX frame is detected. Pluggy in transmitter mode will keep the RS485 driver in input mode.

CRMX will propagate DMX through the system maintaining the input frame rate and frame size with the exception of frame rates that exceed those allowed by the DMX 512-A standard. Different generations of W-DMX modes have individual behaviour in relation to frame rate and synchronisation.

Input DMX frame rates above 830 frames per second will propagate through the system at 830 frames per second to ensure that the DMX output is compliant with the DMX512-A standard.

DMX start code frames

DMX packets with start codes other than the DMX default 0x00 (also known as the Null Start Code, or NSC) and the RDM start code (0xCC) will be propagated through the system, and are subject to the same rules and limitations as the null start code packets. Such frames are called Alternate Start Code, or ASC, frames.

RDM start code frames

Frames with RDM start code (0xCC) are handled separately by transmitters in CRMX systems, as part of the proxy functionality. Transmitters manage the interleaving of RDM frames with null start code packets across the air, and may interleave other RDM frames that are needed to manage the proxy functionality. This may result in RDM frames can appear on the DMX/RDM interface in a different order than on the input of the transmitter.

All RDM frames are handling in compliance with the PLASA E1.20 standard.

Pluggy FX in transmitter nodes discards all frames with RDM start code (0xCC) and RDM draft start code (0xF0).