Standard Single Concentrator Network
MS-5000 Multidrop Concentrator User’s Manual
2-3
2-
M
u
lt
idr
op Com
m
.
The concentrator polls all active devices continuously and inactive devices
intermittently (see “Polling Cycle Timing” on page 2-7).
1
The concentrator polls devices under it by substituting the ASCII hex values
associated with each poll address. It subsequently relays the data to the host
whenever the host is available for input.
Polling Sequence.
In the polling sequence example in figure 2-2, the con-
centrator begins the poll sequence with a RES (reset) followed by poll
address, 1E, the ASCII hex value for Decoder 02.
Figure 2-2 Polling Sequence
It is followed by a REQ (request). The decoder responds by first transmitting
its own address, 1E, followed by a STX (start of text) character, and then the
actual data (a decoded barcode or a noread).
Next it transmits an ETX (end of text) character and an LRC (longitudinal re-
dundancy check) character.
If the concentrator receives the data from the decoder and is able to validate
it with an LRC calculation, the concentrator responds with an ACK (acknowl-
edgment). If the decoder receives the ACK, the decoder ends this successful
exchange with a RES (reset).
Polling Reset Sequences.
Both the concentrator and the decoder can ter-
minate the polling sequence by transmitting a RES (reset) to the other
device. The following conditions and responses apply:
• If the concentrator does not receive a response from the decoder follow-
ing its poll request, the concentrator will wait until it times out and then
retry the request. It will retry the request three times before going on to
another device.
• If the decoder has no information, it responds to a request by transmitting
a RES (reset).
• If the decoder receives a NAK instead of the ACK after transmitting its
data string it will re-attempt to transmit the data string, up to three times. If
1. See also “Polled Device Status Menu” on page 3-15.
R ES 1E R EQ
1E STX DA TA ET X LR C
AC K
R E S
Concentrator
Decoder 02
Start of Sequence
End of Sequence
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...
