2 Protocol description
10
Timing
scheme
A data request runs according to the following timing scheme:
t
0
End marker = 3 characters
(time depending on the baud rate)
t
1
This time depends on the internal processing.
The maximum processing time is 250 ms.
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
2
This time is needed by the slave to change from transmit back to receive.
The master 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: t
2
= 10ms
No data requests from the master are permitted during t
1
and t
2
and during
the slave response time. Data requests made during t
1
and t
2
are ignored by
the slave. Data requests during the response time will result in the invalidation
of all data currently on the bus.
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.
Master
Slave
Data request
Response
t
Data request
t
0
t
1
t
2
t
0
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