Crc Check; Register Address Distribution - Danfoss VFD500 Series Manual

Appendix A Modbuscommunication protocol VFD500 high performance vector control frequency inverter user manual
0x02 Error data address/Illegal
register address
0x03 wrong frame format
0x04 Data is out of range
0x05 Reading request refuse
A.5 CRC check
CRC（Cyclical Redundancy Check）use RTU frame，The message includes an error detection
field based on the CRC method. The CRC field examines the contents of the entire message. The
CRC field is two bytes containing a binary value of 16 bits. It is calculated by the transmission
equipment and added to the message. The receiving device recalculates the CRC of the received
message and compares it with the value in the received CRC field,If the two CRC values are not
equal, there is an error in the transmission.There is a lot of information on the Internet about CRC
checking it is not elaborated hereabout CRC check code generation algorithm,
A.6 Register address distribution
The register address of VFD500 is 16-bit data, the upper 8 bits represent the function code group
number, the lower 8 bits represent the group number, the upper 8 bits are sent before. The 32-bit
register occupies two adjacent addresses, the even address stores the lower 16 bits, and the next
address (odd address) of the even address stores the upper 16 bits.
In the register write operation, in order to avoid frequent damage caused by memory EEPROM
write, using the highest bit of the register address indicates whether it save as EEPROM, the highest
bit to be 1 indicates to save in EEPROM, 0 means save only in RAM. In other words, if you want to
write the register value which is saved after power-off, you should add 0x8000 to the original register
address.
VFD500 register address as follows：
Adress space
0 x 0 0 0 0 ~ 0 x 6 3 6 3
(Function code address
space)
Slave station receives the data address is not allowed
address
the number of registers being Read and write is out of
range
When writing multiple registers, the number of bytes in
the PDU is not equal to the number of registers
Length of frame is not correct
CRC verifying not passed
The data received by the slave exceeds the
corresponding register minimum to maximum range
Operate to read-only register wirte
Operate to read-only register write in running status
Rule: The upper 8 digits of the hexadecimal number indicate the
group number (0 to 99), and the lower 8 digits indicate the serial
number within the group (0 to 99).
Example 1: Function code 27.10 (drive status word 1), which
The hexadecimal address is: 0x1B0A (0x1B = 27, 0x0A = 10),
Decimal address: 27 × 256 + 10 = 6922.
Example 2: Function code 14.01 (digital setting of torque reference),
when no EEPROM is stored, its
The hexadecimal address is: 0x0E01 (0x0E = 14, 0x01 = 1),
The decimal address is: 14 × 256 + 1 = 3585.
If you want to save the content written in communication to EEPROM
after power off, then
The hexadecimal address is 0x8E01 (0x0E01 plus 0x8000),
The decimal address is 36353 (3585 plus 32768).
Note: The addresses calculated in hexadecimal or decimal are the
same, and users can choose a familiar calculation method.
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