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Protocol description
Timing scheme
A data request runs according to the following timing scheme:
Master
Slave
t
End marker = 3 characters
0
(time depending on the baud rate)
t
This time depends on the internal processing.
1
The maximum processing time is 250 ms.
A minimum response time can be set in the device under the menu point item "Interface".
This preset time is the minimum waiting time before an answer is transmitted (0...500
ms). If a smaller value is set, then the response time may be longer than the preset
value (internal processing takes longer), the device answers as soon as internal
processing is completed. The preset time of 0 ms means that the device responds at
the maximum possible speed.
The minimum response time, which can be set is required by the RS485 interface in the
master, to be able to switch over the interface drivers from transmit to receive.
t
This time is needed by the slave to change from transmit back to receive. The master
2
has to observe this waiting time before presenting a new data request. This time must
always be observed, even when the new data request is directed to another device.
RS485 interface:
No data requests from the master are permitted during t
response time. Data requests made during t
during the response time will result in the invalidation of all data currently on the bus.
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Data request
t
t
0
1
t
= 10ms
2
Data request
Response
t
t
0
2
and t
1
and t
are ignored by the slave. Data requests
1
2
t
and during the slave
2
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