Microscan MS-5000, User Manual, Page: 30 / 94

Chapter 2 Multidrop Communications
2-8
MS-5000 Multidrop Concentrator User’s Manual
2-
M
ul
tidro
p Comm
.
Multiple Concentrator Network
Sometimes an additional higher level concentrator is required if for example
you are installing more than fifty decoders in a network.
In this network the lower level concentrators are configured for Multidrop and
assigned multidrop addresses (01 and 02, as shown in figure figure 2-5). Each
lower level concentrator polls its devices, then holds that data until polled by the
higher level concentrator, which in turn relays the data to the host.
Each concentrator has the capability to buffer 18,000 characters.
Note: To allow enough time for data retrieval, LAN Turnaround Timeout for
Concentrator X (see
figure 2-5) must (approximately) be greater than double
LAN Turnaround Timeout for Concentrator 01. For example, if Concentrator 01
is set to the default of 12 ms, try setting Concentrator X to 25 ms (you may need
to experiment to determine the best setting). For more information on Turn-
around Timeout, see page 3-7.
Note: Data output from the higher level concentrator may be slow if the lower
level devices are in a high speed application.
Note: See Table A-4, “Multidrop Address Characters,” on page A-5 for the
translation between hex poll characters and multidrop addresses.
Figure 2-5 Multiple Concentrator Network
Host
Decoder 01
Decoder 02
(Multidrop RS-485 Interface)
Unpolled Protocol
(RS-232 or RS-422 Interface)
Interface)
Decoder 01
Decoder 02
Concentrator
02
First Poll
Sequence
Second Poll
Sequence
Concentrator
X
Decoder 01’s hex poll
character transmitted.
Concentrator 02’s hex
poll character transmit-
ted; decoder 01’s
multidrop address
transmitted.
Multidrop address of
both Concentrator 02
and Decoder 01 trans-
mitted.
Polled Protocol
Concentrator
01