15. Communication Protocol
15.2Basic Structure of Communication Protocol
L7P Drive complies with the MODBUS-RTU Protocoal for communication. For issues not specified in
this manual, please see the related standards (Related Standard: Modbus Application Protocol
Specification 1.1b, 2006.12.28)
In addition, the transmission (Tx) and reception (Rx) concepts are defined in reference to the host.
15.2.1 Transmission/Reception Packet Structure
Maximum length of transmission/reception packet of MODBUS-RTU is 256 Byte. Please make sure the
total length of transmission/reception packet does not exceed 256 byte..
To classify packets, MODBUS-RTU Communication Mode requires emplty spaces of at least 3.5
characters at the starting point and the end point.
Transmission Packet Structure
Additional Functio
Address n Code
Data
Byte
0
1
2
.
.
description
Node ID
Function Data
.
.
Reception Packet Structure
[Normal Response]
Additional Function
Address Code
Data
Byte
0
1
2
.
.
description Node ID Function Data
.
.
[Abnormal Response]
Additional
Address
Byte
0
descripti
on
Node ID
Functio
n Code
1
Function+
0x80
Data
2
Exception code
Error Check
n-1
CRC(MSB)
n
CRC(LSB)
Error Check
n-1
CRC(MSB)
n
CRC(LSB)
Error Check
3
4
CRC(MSB) CRC(LSB)
Protocol Packet CodeDescriptions
Node ID
15-3
