Owners manual
2: Configuring Modbus
Modbus Protocol User Guide 16
Unit ID to IP Address Lookup Table
Figure 2-2. Unit ID to IP Address Lookup Table
These parameters only apply when Modbus Master is selected for the
Serial Protocol. The new menu appears like this:
1) Network/IP Settings:
IP Address . . . . . . . . . . 192.168.100.77
Default Gateway . . . . . . . --- not set ---
Netmask . . . . . . . . . . . --- not set ---
2) Serial & Mode Settings:
Protocol . . . . . . . . . . . Modbus/RTU,Master(s) attached
Serial Interface . . . . . . . 9600,8,N,1,RS232
3) Modem Control Settings:
RTS Output . . . . . . . . . . Fixed High/Active
4) Advanced Modbus Protocol settings:
MB/TCP Exception Codes . . . . Yes (return 0x0A and 0x0B)
Char, Message Timeout . . . . 00050msec, 05000msec
5) Unit ID -> IP Address Table
Close Idle Sockets . . . . . . 10sec
Redundant Entry Retry . . . . Feature Disabled
D)efault settings, S)ave, Q)uit without save
Select Command or parameter set (1. . . 5) to change:
Since serial Modbus uses 8-bit slave addresses and a TCP/IP network requires 32-
bit IP addresses, the IAP Device Server uses this table to map an 8-bit address into
an IP/Unit ID combination. The 8-bit address is used to select the desired IP and as
the Unit ID sent. The table holds 8 entries, and any Modbus slave address not found
in the table returns an exception response to the master (if enabled).
The example below is of adding an entry. Select 5 to edit/view settings.
Figure 2-3. Unit ID to Address Lookup Table Example
Close Idle TCP sockets after (1-60 sec, 0=leave open) (00010)
Redundant entry retries after (15-60 sec. 0=disable feature) (00000)
(Set 4th octet to 0 to use Slave Address as part of IP)
1): 001-100: 192.168.000.000+SLV
2): 101-199: 192.168.000.150
A)dd, D)elete, E)xit - select function A
Modbus addr from (102)
Modbus addr to (102) 255
Slave IP address (192) 172.(168) 16.(000) 123.(000)
1): 001-100: 192.168.000.000+SLV
2): 101-199: 192.168.000.050
3): 200-255: 172.016.123.000+SLV
A)dd, D)elete, E)xit - select function
Close Idle TCP sockets after (3-60 sec, 0=leave open)
Unlike earlier versions of the Lantronix Modbus firmware that tried to hold 8 sockets
open forever, this version only holds sockets open as required. Entering a 0 holds a
single socket open to the last remote Modbus/TCP slave accessed.