LS Industrial Systems Metasol Series - Communication Frame; Modbus; Physical Layer; Protocol

65
E
3. MODBUS
Communication Frame
END
CRC
16bits
START
Char. Time
Address
8bits
Function
8bits
Data
1. Address Range
Valid slave device address range : 0~247 decimal
TRIO Unit address range that is actually used :
1~247 decimal
In case the slave device address of frame where
Master request to Slave is in the range of zero, it is
the address where Master device is broadcasting to
all Slaves.
When Master requests to Slave, transmit address
field after filling it out with corresponding address.
2. Function Range
It displays certain types of function that should be
dealt by slave.
TRIO Unit use 03, 04, 05, and 10 among its function
codes.
In case of no error, Slave turns back the value sent
from Master, otherwise it gives a response after
setting MSB of the value sent from Master as 1.
EX) 0000 0001 0000 0001(normal)
1000 0001(error)
3. CRC Range
Use 2 bits CRC check procedures. Each of 8 bit data’s
result (Address, Function, Data) is accumulated and
CRC checked. Final data checked will be included in
CRC field.
Under RTU Mode, a data is processed on the bit-basis allowing to use only 8 bits when processing one data. More
heavily condensed code will enable RTU Mode to handle large quantity of information comparing with other buses at
the same transferring speed.
When master sends request-frame to slave, slave
sends response-frame.
Protocol
Physical Layer
Asynchronous Format
Baud Rate
Data Bits
Parity
Stop Bit
Communication Method
Communication Port
RS-485
A1 character = 10bit(1 start bit + 8 data bits + 1 stop bit)
9600, 19200, 38400 bps
8 bits
No parity
1 bit
Master - Slave
Data Link Layer
Slave Address
Function Code
Data
CRC
Dead Time
Description
Size
1 byte
1 byte
N byte
2 byte
3.5 bytes transmission time
Slave Address
Definition of Slave action
Additional information
to perform requested
actions from Slave
CRC
SIZEMaster
Device Address
Function Code
Data
Error check
Char. Time
Slave Address
Echo or MSB=1
Requested data or
Exception code
CRC
Response
Slave
Device Address
Function Code
Data
Error check
Digital Trip Relay Accessory