Implemented protocols in echolink one
Softing Industrial Automation GmbH
21
echolink one2PROFINET V. 1.0
15.1.15
If the "Length byte“ is activated (see chapter 8.6), the gateway transfers only the number of bytes
specified there. The number of received Modbus data items is saved in the direction of the field-
bus Master. The length always refers to bytes "Address" to "Dat n" (inclusive in each case),
always without CRC checksum.
8.4.2.2
Data structure
8.4.2.3
Communication sequence
The gateway always acts as the Slave with respect to the fieldbus and always acts as the Master
at the Modbus end. Thus, data exchange must always be started by the fieldbus Master. The
gateway fetches this data which must be structured in accordance with chapter "Data structure“,
from the fieldbus Master, determines the valid length of the Modbus data if the length byte is not
activated, adds the CRC checksum and sends this data record as a request on the Modbus.
The response of the selected Slave is then sent to the fieldbus Master by the gateway - without
CRC checksum. If no response occurs within the stipulated "Response time", the gateway sig-
nals a "TIMEOUT ERROR".
8.4.3
echolink one as MODBUS-Slave
8.4.3.1
Preparation
Before data exchange is commenced, the parameters "Trigger byte" and "Length byte", "Baud
rate", "Parity", "Start bits", "Stop bits" and "Data bits" must be set.
At the rotary switch on the RS-side the MODBUS-ID has to be set, under which the gateway is
addressed in the Modbus.
Since the Modbus operates with a variable data format - dependent on the required function and
data length - but since the fieldbus requires a fixed data length, this must be preset by means of
a selection in the GSDML file. This length should be selected by the user such that the longest
Modbus request resp. response can be processed.
8.4.3.2
Data structure
