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ADS-14221, PPT2 User Manual
RS-485 Multi-drop Network
The RS-485 network consists of a two-wire bus (A and B) that begins at the host processor and
ends at the far end from the processor. A star network configuration can also be used where each
unit is connected directly to the A and B terminals at the host processor. An advantage of the RS-
485 network is that it can extend up to 4,000 feet (1,220 meters) and units can be added and
removed without breaking the network connection. The maximum number of addressable PPT2's on
a network is 89.
A PPT2 multi-drop network connection of six units is shown below. In this network, the device IDs are
not in order from one end of the network to the other. Looking at all the units on the bus, the device
IDs are sequential beginning with ID=01 and without duplication. This is an important setup condition
if global command operation (*99) is desired.
GD = Signal Ground
TD = RS-232 Transmit
RD = RS-232 Receive
A = RS-485(-)
B = RS-485(+)
GD
TD
A
B
RD
ID=03
ID=05
Group=9303
Group=9102
ID=04
ID=02
Group=9302
Group=9101
October, 2016
ID=01
Group=9103
ID=06
Group=9301
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