Toshiba GR-200 Series Instruction Manual page 817

Modbus serial (Modbus RTU)
11.4.4
The serial port (RS-485 module) is provided for the Modbus RTU. The user can set Modbus-
RTU in the IED when the setting [MODBUS_SELECT] = Serial.
Communication
10:48 1/7
LAN
USBCOM
RS485
SLAVE PROTOCOL
IEC61850
IEC103
MODBUS
Figure 11.4-5 Switching to the Modbus RTU (LCD operation)
Note: Both [MODBUS_SELECT] and [MODBUS_ADDR] are displayed when the IED is
ready for the serial communication (i.e., RS-485 port has to be mounted).
Note: The RS-485 for the serial port is mounted on the rear. The user can set a baud rate
(9.6 kbps~57.6, 115.2 kbps), but a default 19.2 kbps is set for the setting
[RS485_1_PAR_SW] (see Figure 11.7-1).
Network structure
(i)
Figure 11.4-6 shows the substation computer is connected with the IEDs by the serial cables,
and daisy-chain method is applied.
RTU master query
IED (Slaves)
Figure 11.4-6 RS-458 serial by Modbus RTU mode
Data link frame
(ii)
The communication is achieved with messages between the substation computer and the IEDs.
Figure 11.4-7 shows query and response messages are transferred with the RTU message
frame.
Start Address field
8 bits
T1-T2-T3-T4
MODBUS
10:48
> MODBUS_BLK
> Off
> MODBUS ADDR
>
> MODBUS_SELECT
>
TCP (➔Serial)
>
Substation computer (Master)
Message frame
Device1 Device2 Device3
Function code field
8 bits
- 798 -
1/3
+
Press
+
2
Press
+
set [MOSBUS_SELECT]=SERIAL
RTU slave response
Data field
N×8 bits
6F2T0200 (0.15)
ENTER key
, , , 
to
Device247
CRC check End
16 bits
T1-T2-T3-T4
GRE200 (1,2)