Eaton Crouse-hinds series - Modbus RTU; Modbus RTU: Read Request (Master); Modbus RTU: Read Response (Slave); Modbus RTU: Single Write Request;Response

88
INM MTL SUM5 Rev 7
DRAFT - 09 June 2021 DRAFT - 09 June 2021
32 MODBUS RTU
The tables below show the standard message formats for data interchange for Modbus RTU
protocol.
RTU tables. Each character represents 8 bit binary data in hexadecimal format.
Y represents a character with more than one possible value.
All characters are framed with 1 start bit, 1 parity bit and 1 stop bit.
32.1 Read Request – Master
RTU
START ADDRESS FUNCTION REGISTER /
COIL
ADDRESS
NO. OF
REGISTERS/
COILS
ERROR
CHECK
STOP
ELAPSED
TIME 3 ½
CHARACTERS
MIN
Y Y YY YY YY
ELAPSED
TIME 3 ½
CHARACTERS
MIN
32.2 Read Response - Slave
RTU
START ADDRESS FUNCTION BYTE
COUNT
DATA ERROR
CHECK
STOP
ELAPSED
TIME 3 ½
CHARACTERS
MIN
Y Y Y YY YY
ELAPSED
TIME 3 ½
CHARACTERS
MIN
32.3 Single Write Request/Response
Master write request and slave write response, are the same.
RTU
START ADDRESS FUNCTION REGISTER /
COIL
ADDRESS
DATA ERROR
CHECK
STOP
ELAPSED
TIME 3 ½
CHARACTERS
MIN
Y Y YY YY YY
ELAPSED
TIME 3 ½
CHARACTERS
MIN