ASCII protocol
The ASCII protocol is a very simple and therefore easy-to-implement protocol.
For the output of the reading result first of all the parameterised start character string,
then the reading result, as an option a character for the code quality and finally the
parameterised stop character string are transmitted. Once the triggering has been
activated via the process interface (dialogue window
, page 46), the
sensor will trigger a reading process on receipt of the character "t" or "T" (ASCII
codes 116
d
and 84
d
).
The ASCII protocol also allows selection of another configuration data file via the
process interface. The characters "p" or "P" (ASCII codes 112
d
and 80
d
) followed by
two numbers (ASCII code 48
d
up to 57
d
) have to be transmitted to the sensor. The
two numbers indicate the number of the selected configuration data file. For exam-
ple, the character sequence "p03" selects the third configuration data file from the
list in the
dialogue page which is used for subsequent
readings.
The trial to select a non-existing configuration data file is ignored by the reader.
Multidrop protocol
The multidrop protocol allows interfacing of several sensors with a master via an RS-
485 bus. An example for interfacing three sensors with one master is shown in the
following figure. In such a network a master can communicate with each sensor indi-
vidually via different commands.
Manage configuration data
Configure trigger
52
RxD-N
TxD-N
RxD-P
TxD-P
Sensor
RxD-N
TxD-N
RxD-P
TxD-P
Sensor
RxD-N
TxD-N
RxD-P
TxD-P
Sensor
RxD-N
RxD-P
TxD-N
TxD-P
Master
