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© Sealevel Systems, Inc.
SeaI/O | SL9049 11/2021
Limiting Expansion Port Communications Data Rate Selection
Limiting Expansion Port Communications Data Rate Selection is not available on older SeaI/O units
(Before Firmware Version 2). In addition, the following modules do not support it:
•
462
•
463
•
470
There are situations where it is desirable to limit the range of allowable data rates or lock down the unit to one
specific data rate. This can be performed by sending the “WriteMultipleRegisters (function 0x16)” MODBUS
command to the unit. Address 302 (decimal) should contain the low order byte of the lower data rate the unit
will accept. Address 303 will contain the high order byte. Note that this command does not cause the rotary
switch to be ignored. Therefore, the rotary switch can be used to reset the defaults range and set the data rate
back to 9600. If this is not desirable, then you can either set the data rate limitation and then set the address
range to prevent the rotary switch from resetting to defaults or you can write to locations 300 through 303 in
one “WriteMultipleRegisters” command.
To reset the unit to “normal” operation, you can issue the MODBUS “Reset Range Settings” (function 0x19).
This setting can also be confi
gured through MaxSSD under the “Advanced” tab, shown below.