Schweitzer Engineering Laboratories SEL-700G Series, Инструкция по эксплуатации

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E.19
Date Code 20170814 Instruction Manual SEL-700G Relay
Modbus RTU Communications
Communications Protocol
7Eh NOP Command
This function code has no operation. This allows a Modbus master to perform
a control operation without any other Modbus command. This is only used
inside of the 7Dh when no regular Modbus query is necessary.
Reading Parameter
Information and Value
Using Modbus
Through use of Modbus commands, you can read the present value of a
parameter as well as parameter name, units, low limit, high limit, scale, and
even the enumeration string (if the parameter is an enumeration type). This
means that you can use a general user interface to retrieve and display specific
parameter details from the relay. Use the 60h, 61h, and 62h commands to
retrieve parameter information, and use the 03 command to retrieve values.
Controlling Output
Contacts Using
Modbus
The SEL-700G includes registers for controlling some of the outputs. See
LOGIC COMMAND (2000h), RESET COMMAND (2001h), and registers in
the Reset Settings region for the control features supported by the relay. Use
Modbus function codes 06h or 10h to write appropriate flags. Remember that
when writing to the Logic command register with output contacts, it is not a
bit operation. You must write all the bits in that register together to reflect the
state you want for each of the outputs.
User-Defined Modbus
Data Region and
SET M Command
The SEL-700G Modbus Register Map defines an area of 125 contiguous
addresses whose contents are defined by 125 user-settable addresses. This
feature allows you to take 125 discrete values from anywhere in the Modbus
Register Map and place them in contiguous registers that you can then read in
a single command. SEL ASCII command SET M provides a convenient
method to define the user map addresses. The user map can also be defined by
writing to user map registers MOD_001 to MOD_125.
To use the user-defined data region, follow the steps listed below.
Step 1. Define the list of necessary quantities (as many as 125).
Arrange the quantities in any order that is convenient for you to
use.
Step 2. Refer to Table E.33 for a list of the Modbus label for each
quantity.
Step 3. Execute SET M command from the command line to map user
registers 001 to 125 (MOD_001 to MOD_125) using the labels
in Table E.33.
Note that this step can also be performed using Modbus
protocol. Use Modbus Function Code 06h to write to registers
MOD_001 through MOD_125.
Step 4. Use Modbus function code 03h or 04h to read the necessary
quantities from addresses 126 through 250 (user map values).
Table E.32 7Eh NOP Command
Bytes Field
An example of a 7D message response using 7E will have the following format:
1 byte Slave Address
1 byte Function Code (7Dh)
2 bytes Status Information
1 byte Function Code (7Eh)
2 bytes CRC-16