User manual

24 Modbus RTU MN744
Parameter Support Continued
Parameter Download
(Sub-Code 4)
This PDU is used to provide parameter download functionality from a host to the drive. Only parameters stored in
the control's EE are downloaded. Only one multi-block Modbus operation may be performed at a time. The
O-scope, parameter upload and parameter download all require multi-block support. They are sent in parameter
index order, each parameter data set taking exactly six (6) bytes: two (2) for parameter number and four (4) for
parameter value. The drive must be disabled before and remain disabled during downloads else a Modbus
Exception results.
Parameter numbers and values are held in a buffer until all parameters have been received by the drive and
there is a CRC match. The drive then attempts to update parameters one at a time in the order received.
Although parameters may be added or subtracted across software versions, so long as a parameter exists its
number and meaning remain unchanged. This allows old parameter files to be downloaded to new drive
software and new parameter files to be downloaded to old drive software. Even if a parameter is rejected by the
drive, a download continues; but after it completes a parameter initialization error is issued.
Each parameter table requires its own download. A block number out of sequence aborts the download.
Request PDU
Host Block 0 (Header Block is first block sent)
Byte 1
Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7 Byte 8 Byte 9 Byte 10
Function Code (67) Sub-Code (4) Block Number Parameter Table Number Parameter Count Blocking Factor Total Blocks CRC
Where,
Byte 1: Parameter Support function code 67 (0x43)
Byte 2: Sub-Code 4 for parameter download
Byte 3: Block number 0 (header)
Byte 4: Parameter Table Number: 1-4
Byte 5-6: Number of parameters
16-bit integer
Data in high to low order
Byte 7: Blocking factor
5 = BF = 40
Maximum number of parameters packed into a PDU
Byte 8: Total number of blocks not counting the header block
Byte 9-10: CRC
Computed over all parameter data value bytes in the download
16-bit unsigned integer
Modbus CRC
Data in high to low order
Host Blocks 1-N (Data Blocks)
Byte 1
Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7 Byte 8 Byte 9 . . .
Function Code (67) Sub-Code (4) Block Number Parameter Number Parameter Value . . .
Byte M-5 Byte M-4 Byte M-3 Byte M-2 Byte M-1 Byte M
Parameter Number Parameter Value
Where,
Byte 3: Block number: 1-N (data)
Bytes 4-5: Parameter number in high to low byte order
Bytes 6-9: Corresponding parameter value in high to low byte order
Bytes M-5 to M: Last parameter and value needed to complete the block
Response PDU: Drive Response
Byte 1
Byte 2 Byte 3
Function Code (67) Sub-Code (4) Block Number
Where,
Byte 1: Parameter Support function code 67 (0x43)
Byte 2: Sub-Code 4 for parameter download
Byte 3: Block Number: 0-N