Appendix I - Multidrop Communications; Figure A-10 Typical Multidrop Network; Figure A-11 Polling Sequence - Microscan MS-615 User Manual

Appendix I — Multidrop Communications
This appendix describes the rules for setting up a concentrator or controller to com-
municate with a scanner in standard Multidrop protocol, as presented in "Protocol,"
on page 2-6.
Figure A-10 shows a typical Multi-
drop network in which 1 to 50 scan-
ners can communicate with a host
via an intermediary device, a con-
centrator or a controller.
Multidrop Addresses
• No two scanners in the Multidrop
Network can have the same
address.
• Each scanner in the network
must have an address (from 01 to
50) assigned in its configuration
program.
Each address has its own separate
poll and select address (from 1C to
7F hex as shown in table A-7 on
page A-18).
For example, during a polling sequence, Scanner 03 expects a 20 hex ("SP"
ASCII poll character) from the concentrator. And during a select command, it
looks for a select value 21 hex ("!" ASCII select character).
Polling Sequence
Data that is transmitted to the host (bar code data, noread messages, counters,
etc.) via concentrators is solicited by poll requests from the host.
Start of Sequence
Concentrator RES 1E REQ
Scanner 02
The polling sequence example in figure A-11 begins with a RES (reset)
from the concentrator followed by poll address 1E (ASCII hex value for
MS-610 Scanner User's Manual
Multidrop Communications
Host
Concentrator
or Controller

Figure A-10 Typical Multidrop Network

1E STX DATA ETX LRC

Figure A-11 Polling Sequence

Polled Protocol
Multidrop ONLY
RS-485 Interface
(LAN)
Scanner 01
Scanner 02
Scanner 03
End of Sequence
ACK
RES
A-15