User Manual of EM760 High-Performance Inverter In addition, for some specific functions, such as register writing (RAM) without EEPROM storage, the user-defined function codes include 0x41 for writing of a single register or command (without saving), and 0x42 for writing of multiple registers or commands (without saving). When the abnormal valid data is received from a device, a related abnormality message will be returned (see 11.3.7 Exception response). The abnormality function code is defined to distinguish the abnormal data from normal communication data. Corresponding to the normal request function code, the abnormality function code = request function code + 0x80 .
Table 10-1 Function Code Definitions of EM760 Series Product PDU parts are detailed in the following sections, depending on various functions. 10.3.3.1 0x03: function code used to read multiple registers or status words In the remote terminal unit, this function code is used to read the content in the continuous block of the holding register. The request PDU describes the starting register address and the number of registers. The register data in the response message is divided into two bytes in each register. The first byte of each register includes high-order bits and the second byte includes low-order bits.
● Request PDU ● Response PDU N* = number of registers ● Error PDU 255 Function code Abnormality function code Function 03 83 This function code is used to read multiple registers or status words. 41 C1 This function code is used to write a single register or command without saving. 42 C2 This function code is used to write multiple registers or commands without saving. 08 88 This function code is used for diagnosis. 06 86 This function code is used to write a single register or command. 10 90 This function code is used to write multiple registers or commands.
Function code 1 byte 0x03 Starting Address 2 bytes 0x0000~0xFFFF Number of registers 2 bytes 1~16 Function code 1 byte 0x03 Number of bytes 1 byte 2×N* Register value N*×2 bytes