92 Network Guide
2-Wire Subnetwork Data Bus
The 2-Wire subnetwork data bus is used to connect ECx-4XX Series I/O Extension Modules to
an ECB-600 or ECL-600 controller. The specifications for this cable are shown in Table 23.
2-Wire Subnetwork Data Bus is Polarity Sensitive
The polarity of the 2-wire subnetwork data bus must be respected as shown in Figure 62. All
terminals identified as SUBNET+ must be connected to the same conductor. Likewise, all ter-
minals identified as SUBNET- must be connected to the same conductor.
2-Wire Subnetwork Data Bus Physical Specifications and Cable Requirements
Cables composed of stranded conductors are preferred over solid conductors as stranded
conductor cable better resist breakage during pulling operations. Distech Controls strongly
recommends the following 2-wire subnetwork data bus cable specifications be respected.
Table 23: Cat 5e Cable Subnetwork Data Bus Physical Specifications and Cable Requirements
Parameter Details
Maximum number of ECx-4XX Series I/O
Extension Modules
2
Subnet ID Addressing Configuration DIP switch located on faceplate. ECx-4XX I/
O Extension Module Addressing on page
95.
Media Shielded, twisted pair
Characteristic impedance 100-130 Ohms
Distributed capacitance Less than 100 pF per meter (30 pF per foot)
Maximum total length of the Cat 5e Cable
subnetwork data bus plus the 2-wire subnet-
work data bus
300 m (1 000 ft.) Maximum – See Subnet-
work Data Bus Length on page 75.
Polarity Polarity sensitive
Multi-drop Daisy-chain (no T-connections, no routers)
EOL terminations Built-in. Must be set / enabled on the last
ECx-4XX Series I/O Extension Module only.
Shield grounding See 2-Wire Subnetwork Data Bus Shield
Grounding Requirements on page 94.
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