german:     DMX Interface Hardware: this is a complete step-by-step description how to access the hardware, and how to set the working parameters required for DMX512/1990. Find memory maps, hardware addresses and other hardware-related stuff.   
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512ch DMX Send Card
512ch DMX Send Card
512ch opto-isolated card
10124ch DMX Read/Write Card
DMX PrinterPort Interface
DMX Serial Port Interface
DMX USB Port Interface
PCMCIA DMX Interface Card

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Hardware Description

SERIAL PORT / DMX INTERFACE DMXSPI

[Serial / DMX Interface DMXSPI]

THE PMX PROTOCOL

SERIAL FORMAT

9600 baud, 1 start bit, 8 data bits, 1 stop bit, no parity. The data stream may be fully packed.

CABLE

For RS232 operation, as with the 4102A, single core screened cable may be used. MAXIMUM LENGTH for RS232 communication is 100m.

TERMINATION

line termination is NOT required.

BRANCHING

no problem.

HANDSHAKING

not required - so RTS (Pin E or 5 on a BBC Micro or pin 4 on a 25 pin `D' connector) and CTS (Pin D or 2 on a BBC Micro or pin 5 on a 25 pin `D' connector) need to be cross linked at the computer.

RESOLUTION

up to 14 bits possible, but normally 8 bits (256 possibilities, this is used with the PMX/DMX conversion), older products used 7 bits (128 possibilities).

NO OF CHANNELS

theoretically 15,360 max. The protocol allows 128 pages of 120 channels each. The 4102A is limited to 4 pages (480 channels total).

REFRESH

is not required. Data is latched by the receiving device. Only the changes need to be transmitted. However it is good practice to send the constant Levels and the Page Number from time to time- for example, when there are no changes to send.

TRANSMISSION PROTOCOL

Address

A byte with bit 7 set is an Address i.e. a Channel Number. Channels Numbers in the range 1-120 are sent as 128-247. Channels Numbers in the range 121-240 are sent as 128-247 after having first changed the Page Number from 0 to 1 see below.

Level

A byte with bit 7 clear is a Level. ONE or TWO Level bytes with values of 0-127 follow an Address.
For 7 bit resolution, only ONE byte need be sent.
For 8 bit resolution, where bit 0 is Lo, only ONE byte need be sent.
For 8 bit resolution, where bit 0 is Hi TWO bytes need to be sent with bit 6 of the second byte set. For future expansion, bit 5 to bit 0 of the second byte could be used, giving up to 14 bit resolution. If only ONE Level byte is sent, it will not be acted upon until the next Address is received.

Bytes 248 to 255 are used for special codes: 248 sets all channels to the Level which follows e.g. 0 for Blackout. 249 changes Page Number to the ONE Level byte which follows (0-127). Each of the 128 possible pages allow you to address 120 channels. Receiving units default to page 0 (channels 1-120) at switch on. The Page Number remains in the new page until another 249 sequence is sent. 250-255 are reserved by Pulsar to send ASCII, Key Presses, Slider Moves & other Controller to Controller information.

back to 4102A Hardware Description

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