Pilz PNOZ mmc1p ETH - Manual (Page 38)

4.2 Data exchange via Modbus/TCP
4 Application example
Pilz GmbH & Co. KG, Felix-Wankel-Straße 2, 73760 Ostfildern, Germany
Telephone: +49 711 3409-0, Telefax: +49 711 3409-133, E-Mail: [email protected]
4-2
4.2 Data exchange via Modbus/TCP 4200 Data exchange via Modbus/TCP 4- ModbusTCP_Bsp_Kommunikation Client - Server
An example of data exchange is shown below. The modular safety sys-
tem PNOZmulti is always the server in a connection and the PSSu sys-
tem from the automation system PSS 4000 is always the client in a
connection.
It is always the connection's client that initiates data transfer. The direc-
tion of the data flow (send/receive) and access to Modbus/TCP data ar-
eas (coils, discrete inputs, input registers, holding register) is defined by
the function code.
When sending, the connection's client sends data to a data area belong-
ing to the connection's server. This is also known as "Writing data".
When receiving, the connection's client requests and receives data lo-
cated in a data area belonging to the connection's server. This is also
known as "Reading data".