Schweitzer Engineering Laboratories SEL-700G1 - Table E.29 61 H Read Parameter Enumeration Text Query Error Messages; Table E.30 7 Dh Encapsulated Packet with Control Command; Table E.31 7 Dh Encapsulated Packet Query Errors

E.18
SEL-700G Relay Instruction Manual Date Code 20170814
Modbus RTU Communications
Communications Protocol
The relay responses to errors in the query are as follows:
7Dh Encapsulated
Packet With Control
Command
The SEL-700G uses this function to allow a Modbus master to perform
control operations and another Modbus function with one query. The Device
Net card transmits this command periodically to achieve high-speed I/O
processing and establish a heartbeat between the DeviceNet card and the main
board.
Table E.31 shows the format of the relay responses to errors in the query.
Table E.29 61h Read Parameter Enumeration Text Query Error Messages
Error Error Code Returned
Communications
Counter Increments
Illegal parameter to read Illegal Address (02h) Invalid Address
Illegal enumeration in index Illegal Data Value (03h) Illegal Register
Table E.30 7Dh Encapsulated Packet With Control Command
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (7Dh)
2 bytes Control Command (same as write to 2000h)
1 byte Embedded Modbus Function
n bytes Optional Data to Support Modbus Function (0–250)
2 bytes CRC-16
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (7Dh)
2 bytes Status Information (Register 2100h or 2101h
based on Bit 3 in Control Command Word)
1 byte Embedded Modbus Function
n bytes Optional data to support the Modbus function (0–250)
2 bytes CRC-16
Table E.31 7Dh Encapsulated Packet Query Errors
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (7Dh)
2 bytes Status Information (Register 2100h or 2101h based on Bit 3 in
1 byte Modbus Function with Error Flag
1 bytes Function Error Code
a
a
If the embedded function code is invalid, then an illegal function code is returned here and
the illegal function counter is incremented. This error code is returned by the embedded
function for all valid embedded functions.
2 bytes CRC-16