5.0 ECL 296 / 310 Modbus network specication
The ECL 296 / 310 Modbus physical layer interface is supported by
the half duplex RS485 interface (A, B, common signal - i.e ref GND).
1. Maximum trunk (Bus) length = 1200 meters for AWG24
(0,51mm diameter) copper (less AWG= bigger diameter: is bet-
ter).
Note: AWG= American wire gauge (AWG).
2. Maximum number of nodes in the network = 32 (including
master node, ECLs and repeater node).
Note: Each repeater node is capable of driving another 32
nodes (including repeater node) of 1200 meter.
I.e. 30 ECLs between two repeater stations (or) 31 ECLs in the
network connected to master node / repeater node. Refer the
gure below.
3. Maximum derivation cable length per node (per ECL) = 1,25
meters (calculated based on 40 m max. derivation cable length
for 32 nodes).
4. Line termination (to ensure the communication quality) = At
each extremity of the trunk cable (150 ohms (or) 120 ohms, 0,5
watts resistor at both ends.
Note: Repeaters are having internal termination resistors which
can be “switched on/ switched OFF” by the user.
a.
If “repeaters” are used in the extremity of the trunk cable, then
switch on the repeater termination (striped block, represented
by 3):
b.
If “repeaters” are used to make a branch from one of the interme-
diate nodes, then do not switch on the “repeater termination”
(unstriped block connected to ITr cable).
1) = surge protector
2) = repeater
3) = line termination (LT)
c.
If the ECL is used in the extremity node of the trunk cable, connect
an external line termination (150 ohm / 120 ohm, 0,5 watts resis-
tor).
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