Servomex 07931001B, Руководство оператора

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© Servomex Group Limited. 2020 07931001B revision 6
Exception codes
If an error should occur while processing a message one of the following exception codes
will be returned by the instrument.
Code Condition Meaning
01 Illegal function Requested function code is not supported.
02 Illegal data address The combination of data address and transfer
length is invalid for this function.
03 Illegal data value A value contained in the query data field is not an
allowable value. This indicates a fault in the
structure of the remainder of a complex request.
This does NOT mean that a value to be stored in a
register is incorrect as Modbus has no means of
determining what is legal for any particular
register.
04 Slave device failure An unrecoverable error occurred while the unit
was attempting to perform the requested action.
Addressing
Addresses in Modbus ADU (application data unit), run from 1
–
N, whereas addresses in
the Modbus PDU (protocol data unit) run from 0
–
N. This appendix gives addresses in the
ADU model. Depending on the particular Modbus master, addresses may have to be
entered as they are given or have 1 subtracted from them. For example, to read
register 101 an address of 100 may be needed.
Note: Slave ID: 247
Floating point numbers
Floating point numbers (e.g. 12.34,
–
1012.32, etc.), are digitally represented using the
IEEE
–
754 format. Single precision floating point numbers are used throughout and they
require 32 bits of data. Since a Modbus register holds 16 bits it takes 2 registers to
represent a floating-point number. We default to having the most significant word of the
float, bits 16
–
31, in the first register, and the least significant word, bits 0
–
15, in the next
register. This order can be reversed by setting a coil in the system control mapping.