Schweitzer Engineering Laboratories SEL-701, Instruction Manual

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Date Code 20010719
701 Motor Protection Relay
Modbus
®
RTU Communications Protocol
Modbus RTU Communications Protocol
C.3
Supported Modbus Function Codes
The SEL-701 Relay supports the Modbus function codes shown in Table C.2 .
Table C.2 SEL-701 Relay Modbus Function Codes
Modbus Exception Responses
The SEL-701 Relay sends an exception code under the conditions described
in Table C.3 .
Table C.3 SEL-701 Relay Modbus Exception Codes
Table C.2 SEL-701 Relay Modbus Function Codes
Code Description
01 Read Coil Status
02 Read Input Status
03 Read Holding Registers
04 Read Input Registers
05
a
Force Single Coil
06
a
Preset Single Register
07 Read Exception Status
08 Loopback Diagnostic Command
10h
a
Preset Multiple Registers
a
The SEL-701 Relay supports broadcast operation for these function codes. Broadcast
function codes use slave device address 00h. Slave devices do not send a response to
broadcast functions.
Table C.3 SEL-701 Relay Modbus Exception Codes
Exception
Code
Error Type
Description
1 Illegal Function Code The received function
code is either undefined or unsupported.
2 Illegal Data Address The received command contains an
unsupported address in the data field.
3 Illegal Data Value The received command
contains a value that is out of range.
4 Device Error The SEL-701 Relay is in
the wrong state for the requested function.
6 Busy The SEL-701 Relay is unable to process the
command at this time due to a busy resource.
8 Memory Error There is a checksum error on the stored data.