GE B30 Communications Manual

Also see for b30: Maintenance manual Instruction manual Instruction manual Instruction manual Communications manual

Contents

2-6 UR FAMILY – COMMUNICATIONS GUIDEMODBUS FUNCTION CODES CHAPTER 2: MODBUS COMMUNICATION2Table 2-8: Master and slave device packet transmission example2.2.5 Store multiple settings (function code 10h)This function code allows the master to modify the contents of a one or more consecutive setting registers in a relay.Setting registers are 16-bit (two byte) values transmitted high order byte first. The maximum number of setting registersthat can be stored in a single packet is 123. The following table shows the format of the master and slave packets inModbus RTU. Modbus TCP/IP ADUs have a MBAP instead of slave address, and CRC is in another stack layer. The exampleshows a master device storing the value 200 at memory map address 4051h, and the value 1 at memory map address4052h to slave device 11h (17 decimal).Table 2-9: Master and slave device packet transmission example2.2.6 Exception responsesProgramming or operation errors usually happen because of illegal data in a packet. These errors result in an exceptionresponse from the slave. The slave detecting one of these errors sends a response packet to the master with the high orderbit of the function code set to 1.The following table shows the format of the master and slave packets in Modbus RTU. Modbus TCP/IP ADUs have a MBAPinstead of slave address, and CRC is in another stack layer. The example shows a master device sending the unsupportedfunction code 39h to slave device 11h.Master transmission Slave responsePacket format Example (Hex) Packet format Example (Hex)SLAVE ADDRESS 11 SLAVE ADDRESS 11FUNCTION CODE 06 FUNCTION CODE 06DATA STARTING ADDRESS - high 40 DATA STARTING ADDRESS - high 40DATA STARTING ADDRESS - low 51 DATA STARTING ADDRESS - low 51DATA - high 00 DATA - high 00DATA - low C8 DATA - low C8CRC - low CE CRC - low CECRC - high DD CRC - high DDMaster transmission Slave responsePacket format Example (Hex) Packet format Example (Hex)SLAVE ADDRESS 11 SLAVE ADDRESS 11FUNCTION CODE 10 FUNCTION CODE 10DATA STARTING ADDRESS - hi 40 DATA STARTING ADDRESS - hi 40DATA STARTING ADDRESS - lo 51 DATA STARTING ADDRESS - lo 51NUMBER OF SETTINGS - hi 00 NUMBER OF SETTINGS - hi 00NUMBER OF SETTINGS - lo 02 NUMBER OF SETTINGS - lo 02BYTE COUNT 04 CRC - lo 07DATA #1 - high order byte 00 CRC - hi 64DATA #1 - low order byte C8DATA #2 - high order byte 00DATA #2 - low order byte 01CRC - low order byte 12CRC - high order byte 62