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2301E Digital Control Manual 26641
140 Woodward
2301E Control Modbus Addresses
The Modbus communication ports in the 2301E are programmed for unique
Modbus addresses. A complete listing of these addresses for your application is
located at the end of this section in the manual. The Modbus address listing
consists of Boolean Writes, Boolean Reads, Analog Reads and Analog Writes. The
Boolean reads and writes are also referred to as input and holding coils. The
analog reads and writes are also referred to as input registers and holding
registers. All values that can be addressed by Modbus are considered to be
discrete and numeric. The discrete values are a 1 bit binary, on or off value and the
numerics are 16 bit values. Discrete values are sometimes referred to as coils or
digitals and numerics are referred to as registers or analogs. All read/write registers
are interpreted by the 2301E as signed 16 bit integer values. Since Modbus can
only handle integers, values that require a decimal point in the Modbus Master
Device are multiplied by a scaling constant before being sent by the 2301E. See
Appendix B for the default communication constants and ranges.
Boolean Writes
Boolean Writes are logic signals that are writable to the 2301E control. An
example of a Boolean write value would be raise or lower commands. A logical
true denoted by the value 1 will cause the command listed in the description to
be executed.
If a RUN (address 0.0002) command is given it will be latched. To reset the latch
remove the RUN contact and give a command to STOP (address 0.0003). This is
applicable for the following commands:
0.0002 Run (latch)
0.0003 Stop (reset latch)
0.0004 Failed Speed Override ON (latched)
0.0005 Failed Speed Override OFF (reset latch)
0.0006 Rated (latched)
0.0007 Idle (reset latch)
0.0010 Isoch (latched)
0.0011 Droop (reset latch)
0.0012 Baseload ON (latched)
0.0013 Baseload OFF (reset latch)
Boolean Reads
Boolean Reads are logic signals that are readable from, but not writable to, the
2301E. An example of a Boolean read value would be a turbine trip status
indication. The logic true will have the value 1 if the statement in the description
column is true and a 0 if false. The ‘1:’ term in the address identifies a logic true.
The 2301E supports Modbus function code 2, which involves reading selected
logic signals.