OP7100
Hardware 41
Any Rabbit Semiconductor controller or the OP7100 can be a master or a
slave. A network can have up to 255 slaves, but only one master.
A multidrop network requires termination/bias resistors to minimize reflec-
tions (echoing) and to keep the network line active during an idle state. The
OP7100 termination resistors are already installed, and by default are en-
abled by having jumpers installed on header J9. Remove the jumpers from
header J9, as shown in Figure 3-21, to disable or remove the termination
resistors. Only the first and last devices on a multidrop RS-485 network should
have the termination resistors enabled.
Figure 3-21. Enabling/Disabling Termination Resistors
Only a single, solid conductor should be placed in a screw clamp terminal.
Bare copper, particularly if exposed to the air for a long period before
installation, can become oxidized. The oxide can cause a high-resistance
(~20
Ω
) connection, especially if the clamping pressure is not sufficient.
To avoid oxidation, use tinned wires or clean, shiny copper wire. If you are
using multiple conductors or stranded wire, consider soldering the wire
bundle or using a crimp connector to avoid a later loss of contact pressure
to a spontaneous rearrangement of the wire bundle. Note that soldering a
stranded wire may make the wire subject to fatigue failure at the junction
with the solder if there is flexing or vibration.
FD
Termination Resistors
Enabled
Termination Resistors
Disabled
J10
J9
1
2
3
4
J9
1
2
3
4
J9
Summary of Contents for OP7100
Page 1: ...OP7100 Serial Graphic Display User s Manual 019 0065 070831 O ...
Page 10: ...OP7100 x About This Manual ...
Page 16: ...OP7100 16 Overview ...
Page 74: ...OP7100 74 Software ...
Page 82: ...OP7100 82 Graphics Programming ...
Page 88: ...OP7100 88 Installation ...
Page 98: ...OP7100 98 Specifications ...
Page 108: ...OP7100 108 Memory I O Map and Interrupt Vectors ...
Page 112: ...112 Serial Interface Board 2 OP7100 ...
Page 113: ...OP7100 Backup Battery 113 APPENDIX E BACKUP BATTERY ...
Page 116: ...OP7100 116 Backup Battery ...
Page 124: ...OP7100 124 Index ...
Page 126: ...XX0000 Schematics ...