Standard Single Concentrator Network
MS-5000 Multidrop Concentrator User’s Manual
2-7
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Polling Cycle Timing
A properly connected decoder or other device, configured for Multidrop and
assigned an address between 01 to 50, will be listed in the concentrator’s
Device Status menu as Active.
During the polling cycle, the concentrator polls each active decoder for label
data and checks one inactive address (
slow poll
) to determine if it has
become active. If so, it will be added to the Active list. Within a given num-
ber of polling cycles, all 50 decoder addresses are polled. This routine
keeps polling cycles as brief as possible and allows any addressable device
to be turned on or off during the polling operation without stopping or re-
configuring the concentrator. The time it takes to poll an inactive device will
be slightly greater than the Turnaround Timeout setting, which by default is
12 ms.
For a given baud rate, it would seem that a simple multiplication of total
characters times baud rate could be used to predict the duration of a polling
cycle. This is not the case, as evidenced in figure 2-4 which shows that the
actual time of 582 ms to poll 200 characters (25 decoders times 8 charac-
ters each) is almost 3 times the time it should take to transfer 200 charac-
ters at 9600 baud. The rest of the time can be accounted for by overhead:
addresses, STX, ETX, and LCR characters, etc. Add to this the slow poll
routine which varies depending on the number of inactive devices and the
distribution of active addresses, and it becomes clear that any formula you
may derive will be imprecise and generally limited to your particular set of
parameters.
Figure 2-4 Polling Cycle Durations for 25 Active Decoders
W ith no label
W ith 8 charactres
from each decoder
38.K
baud
9600
baud
57.5 m s
195 m s
125 m s
582 m s
0
100
200
300
400
500
600
Polling cycle duration (in m illseconds)
Summary of Contents for MS-5000
Page 1: ...MS 5000 Multidrop Concentrator User s Manual P N 83 005000 REV J...
Page 8: ...viii MS 5000 Multidrop Concentrator User s Manual...
Page 52: ...Chapter 3 Menu Configuration 3 18 MS 5000 Multidrop Concentrator User s Manual 3 Serial Config...
Page 66: ...Chapter 4 Serial Commands 4 14 MS 5000 Multidrop Concentrator User s Manual 4 Operations...
Page 90: ...A 14 MS 5000 Multidrop Concentrator User s Manual Appendices...
