Optelecom 9525AY, Installation And Operation Manual

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2.2.2 Local Daisy Chain Mode
In this mode, there is a specific "upstream" and "downstream" data direction, because data is only
transmitted to or from the master and not both directions on a ring. Specifically, the TX1/RX1 port
communicates upstream to the master controller and the TX2/RX2 port communicates downstream to
the next modem on the daisy chain. The local daisy chain mode is not fault tolerant. Optical data
received from the master via TX1/RX1 is re-timed, retransmitted downstream via the TX2/RX2 port and
output as RD on the data port. Anti-streaming on the TX1/RX1 port is disabled because it would serve
no purpose. Optical data received from the next modem downstream via the TX2/RX2 port is re-timed
and retransmitted upstream to the master controller via the TX1/RX1 port. Data received via the
expansion port input TDE from a modem feeding a branch, and from the TD input of the data port are
ORed with the data from the TX2/RX2 port to be transmitted back to the master via the TX1/RX1 port.
Anti-streaming is an option on the TX2/RX2 port in this mode.