Datum bc632D, User Manual

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INSTALLATION AND SETUP
Datum Inc bc632D Wall Mount LED Display (Rev A) 2-9
2.3.1 DIGITAL TIME PROTOCOL
The bc632D Wall Display has the capability of operating in a Master/Slave mode in which Slave
bc632D's synchronize digitally to the timebase of a Master bc632D. This allows computer
synchronization of two or more displays without external time code. Synchronization accuracy’s of
±
1
microsecond can be achieved between the Master and Slaves. The Master/Slave mode of operation is
summarized as follows:
•
A Master bc632D decodes its selected time source. A 1PPS synchronization pulse and 9600 baud
serial time message (days - seconds) is broadcast via two RS-485 lines each second through the
TX side of the RJ11 connector (J3). The Master automatically broadcasts these digital time signals
when decoding time or flywheeling.
•
Slave bc632D's are programmed with "Digital Time" as their time source. The RX side of the
Slave's RJ11 connector (J3) is connected to the TX side of the Masters RJ11 with four-conductor
telephone cable. When a valid 1PPS and time message is received from the Master,
synchronization takes place. All features of the bc632D are available with this mode including
"flywheeling." (Refer to Figures 2-9 and 2-10.) The signal received on the slaves RX connector
are looped through to the TX connector, allowing signs to be connected in a "daisy-chain" fashion.
•
Terminate the RS-485 line with the bc632D's termination resistors by moving the existing jumper on
JP5 pins 1 and 2 to JP5 pins 3 and 4. (See Section 2.1.7). The two bc632D's on the end of the
network should be terminated.
Note : On a Master\Slave bc632D network only two modules should be terminated.
•
Any one of the bc632D's depicted in Figures 2-5 and 2-6 can serve as a Master. The Master is
the only unit in the network that transmits Time and Synchronization pulses on the serial lines. See
Section 3.3.10 for a description of how to set the display as a master. If more than one bc632D
tries to operate as a Master, the time signals are corrupted. There is not any hardware damage
when this occurs, but network synchronization is not possible. When a bc632D is designated as a
Slave (Refer to step 2) all drivers are disabled.