GE PanaFlow MV80, User Manual, Page: 103 / 164

PanaFlow™ MV80 & MV82 User’s Manual 91
Chapter 4. Serial Communications
4.2.6j Error Responses
If an error is detected in the message received by the unit, the function code in the response is the received function
code with the most significant bit set, and the data field will contain the exception code byte (see
Table 13 below).
If the first byte of a message is not equal to the unit's Modbus address or if the unit detects a parity error in any
character in the received message (with even or odd parity enabled) or if the message CRC is incorrect, the unit will not
respond.
4.2.6k Command Message Format
The start address is equal to the desired first register number minus one. The addresses derived from the start address
and the number of registers must all be mapped to valid defined registers, or an invalid data address exception will
occur.
4.2.6l Normal Response Message Format
4.2.6m Exception Response Message Format
Table 13: Exception Codes
Exception Code Description
01 Invalid function code - function code not supported by device.
02 Invalid data address - address defined by the start address and
number of registers is out of range.
03 Invalid data value - number of registers = 0 or >125,
or incorrect data with the Write Single Coil command.
Table 14: Address Register Mapping
Device Address Function Code Start Address N = No. of Registers CRC
8 bits, 1...247 8 bits 16 bits, 0...9998 16 bits, 1...125 16 bits
Table 15: Normal Response Message Format
Device Address Function Code Byte Count = 2 x N Data CRC
8 bits, 1...247 8 bits 8 bits (N) 16-bit registers 16 bits
Table 16: Exception Response Message Format
Device Address Function Code + 0x80 Exception Code CRC
8 bits, 1...247 8 bits 8 bits 16 bits