Connecting The Line Cables - Hitachi IR.Station Hardware Manual

5 CABLING

5.2 Connecting the Line Cables

Always terminate the CPU module (master station) and the IR.Station module which are at
both ends of the line. The terminating resistance is 120 ohms (built-in) or any (externally
connected). When using an external terminating resistor, select it according to the
characteristic impedance of the cable.
Always follow the cabling instructions to connect cables correctly. If the cable connection
is wrong, the module communication may be disabled. For details, see 5.2.1.
Ground one SHD terminal per cable. Do not ground the FG terminal of every unit.
The cable lengths are dependent upon transmission speeds: 240 m or shorter at 1.0 Mbps,
480 m shorter at 0.5 Mbps, 800 m or shorter at 0.25 Mbps, and 1000 m or shorter at 0.125
Mbps. Select optimum cable lengths according to the transmission speeds of the system.
Use the cables of the same size and ampacity on an identical line. If the sizes and
ampacities of the cables are not the same, the system operation cannot be assured.
Assign unique station numbers to the units.
CPU unit
Must be
IR.LINK
terminated here.
(LQE046)
I/O unit-1
IR.Station
(LQS021)
- 28 -
I/O unit-2
IR.Station
(LQS021)
I/O unit-N
N≦31
IR.Station
(LQS021)
Must be
terminated here.