D374-20-880 Issue E
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Installation
3.6 Serial Interface Performance
The iTIM has to process both the LON network messages (that arrive when sent by the pumping system) and the serial
messages. It is not possible to provide definitive performance figures for the serial interface as it will vary with time
according to the pumping system configuration and operation. However, the following information is provided to
assist in programming your control equipment for optimum operation with the serial interface.
z The pumping system sends data from each object at relatively low frequencies, usually regularly at 3, 7, 15
or 45 second intervals. Messages are also sent by the pumping system when there is a sudden change in
status.
z At 9600 baud, each character in a command/query message or the corresponding reply message will take
approximately 1ms. The response for a query takes, typically, 30 to 50ms.
z Command messages can take several seconds to be actioned, as a serial response is sent that is, the
command message is sent to the pumping system through the LON network, then the pumping system must
action the message.
z We recommend that you do not send a command/query message until the reply message from the previous
command/query message has been received. A small delay of 100ms will allow the iTIM to process any LON
messages, and to carry out internal ‘housekeeping’.
z If the serial link is overloaded, the worst effect will be that the iTIM will miss a data update from the
pumping system, however, the new data will then be provided by the pumping system at the next regular
update. There will be no direct effect on the operation of the pumping system.
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