Toshiba GR200 Series Instruction Manual

Also see for GRB200: Instruction manual

6F2S1931 (0.20)Centralized GRB200(Soft: 030, 031, 032, 033, 034)- 625 -10.5.4 Modbus serial (Modbus RTU)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.Communication10:48 1/7LAN >USBCOM >RS485 >SLAVE PROTOCOL >IEC61850 >IEC103 >MODBUS10:48 1/3MODBUS_BLK +OffMODBUS ADDR +2MODBUS_SELECT +TCP (Serial)MODBUS >Press , , ,  toset [MOSBUS_SELECT]=SERIALPress ENTER keyFigure 10.5-5 Switching to the Modbus RTU (LCD operation)Note: Both [MODBUS_SELECT] and [MODBUS_ADDR] are displayed when the IED isready 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 10.7-1).(i) Network structureFigure 10.5-6 shows the substation computer is connected with the IEDs by the serial cables,and daisy-chain method is applied.Substation computer (Master)Device1RTU master queryRTU slave responseRS-458IED (Slaves)Device2 Device3 Device247Message frameFigure 10.5-6 RS-458 serial by Modbus RTU mode(ii) Data link frameThe communication is achieved with messages between the substation computer and the IEDs.Figure 10.5-7 shows query and response messages are transferred with the RTU messageframe.T1-T2-T3-T4Address field8 bits 8 bitsFunction code field Data fieldN×8 bitsCRC check16 bitsStartT1-T2-T3-T4End