DEUTSCHMANN AUTOMATION UNIGATE CL ProfibusDP, Инструкция по эксплуатации

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Implemented protocols in UNIGATE CL with Universal Script Deutschmann Automation GmbH & Co. KG
26 UNIGATE fieldbus gateway UNIGATE CL - ProfibusDP V. 2.3 17.6.10
10.4.2.2 Data structure
10.4.2.3 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".
10.4.3 UNIGATE as MODBUS-Slave
10.4.3.1 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 GSD file. This length should be selected by the user such that the longest Mod-
bus request resp. response can be processed.
10.4.3.2 Data structure
10.4.3.3 Communication sequence
The gateway always acts as the Slave with respect to the fieldbus and also acts as Slave at the
Modbus end. A data exchange is always initiated by the MODBUS-Master via the RS-interface. If
the Modbus-address (1st Byte) which is sent out by the Modbus-Master is identical with the
address set on the gateway, the gateway sends the received data (without Modbus-address and
CRC-check sum) to the fieldbus-master (look picture above). With it the gateway optionally com-
pletes as an introduction a Trigger byte and a Length byte.