USER MANUAL – Z-PASS1/Z-PASS2
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Modbus Bridge
Z-PASS can be configured to run as a Modbus Bridge: Modbus TCP requests received from both the
Ethernet interface and the PPP (Mobile Network) interface are converted into Modbus RTU requests and
sent to the serial interface; in the same way, the Modbus RTU responses received from the serial interface
are converted to Modbus TCP responses and sent back to the source network interface.
A Modbus Bridge instance can be activated for each of the three available serial ports: COM1
(RS232/RS485), COM2 (RS485) and COM4 (RS485); each one can receive the Modbus TCP requests on a
different TCP port (e.g.: 501, 502, 503).
Another possible configuration is to run a Modbus Bridge instance, receiving Modbus TCP requests on a
single TCP port (e.g.: 502) and handling two or all the three serial ports. In this case, Modbus RTU requests
are simultaneously sent to all the configured ports; obviously, in this configuration, each slave module on
the two or three buses shall have a distinct Modbus address;
Each Modbus Bridge instance can support up to 32 simultaneous TCP connections.
The TCP connection can be established over a VPN tunnel, as shown in the following figure.
A detailed description of the Modbus Bridge configuration can be found in 18.4.1 paragraph.
