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Install Op and Diags for MIU Modems and RS485 (0049-0002-010A) Page 5 of 16
5. RS485 SPECIFICATIONS
MIUXXXX/485 are low-power Transceiver for RS485 and RS422 communication
Features: Point to Point or Multidrop/Multipolling
Full or Half Duplex
Drivers are short - circuit current limited & protected against excessive
power
dissipation (shutdown will places the drivers in a high - impedance state).
When Drivers are disabled (by TXD), drivers will switch to high
impedance state.
Note in two-wire or multi-drop/multi-polling networks TX enable by TXD
should be active
Receiver input impedance is 12K ohms.
Reduced slew- rate drivers that minimize EMI and reduce reflections
caused by improperly terminated cables This will allow error - free
transmitted data up to 200Kbps
RS485/RS422 standard covers line lengths up to 4000 feet. For line
lengths
greater than 4000 feet a line repeater can be added.
MIUXXXX/485 can drive 4000 feet of 26AWG twisted - pair cable at
200k bps into 120 ohms load.
To minimize reflections, the line should be terminated at both ends. In
multi - polling/multi - drop environments (up to 32 drops) all drops off
the main cable should be as short as possible.
Only the Master/Host unit and the end of cable unit should be terminated.
Typical Speed versus Distance - (4-wire point to point 26 AWG twisted cable)
SPEED DISTANCE
1200bps 6.0 miles(9.6 km)
2400 bps 4.5 miles (7.2 km)
4800 bps 4.0 miles (5.5 km)
9600 bps 2.5 miles (4.0 km)
19,200 bps 1.8 miles (2.9 km)
38,400 bps 1.4 miles (2.1 km)
56,400 bps 1.1 miles (1.8 km)
115,000 bps 0.6 miles (0.9 km)
NOTE: Speed and distances will depend on actual operating
environment.
6. ENVIRONMENTAL SPECIFICATIONS
The CIU/485 (MIUXXX\485) meets the following environmental specifications.