B722-40-880 Issue H
Page 30
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Installation
Figure 9 - Schematic diagram of the logic interface connections
3.7.7
Multi-drop mode
Using multi-drop mode, a single computer system can communicate with more than one DX pump. Each DX pump
must be assigned its own individual address before it can be fitted into a multi-drop system. The command to assign
the multi-drop address is sent in standard DX message format (as detailed in
.
The message protocol in multi-drop mode is marginally different to that described for serial messages in single pump
systems. The main differences in multi-drop message protocol are detailed below:
All multi-drop commands, queries or replies have the first character
#
.
All commands, queries and replies contain a header containing the address of the node that the message is
to, followed by the address of the node that the message is from.
There is a delimiter character: (colon) which separates the two multi-drop addresses in the header.
The remainder of the message (command, query or reply) follows the same protocol as already described for
single pump systems.
The wild card address 99 is very useful and means ‘any’ node.
1. RS232 interface on control equipment
2. 24 V d.c. electrical supply
3. Fuse
4. Optional LED indicator - system OK
5. Optional LED indicator - normal speed
6. Current limit resistor for LED
7. Optional serial mode selector
8. DX pump
9. Optional voltmeter
10. Optional serial enable switch
11. Optional standby switch
12. Start switch
