Nidec Unidrive M300 - Page 138

138 SI-Ethernet User Guide
Issue: 3
Table 7-5 Start register addressing
7.2.7 FC03 – Read multiple registers
This function code allows a contiguous array of registers to be read. The maximum number of
registers that can be read is 120, this allows up to 120 16-bit parameters or 60 32-bit parameters
to be read in a single transaction. If this is exceeded the server will issue an exception response
code 2.
Master request data Slave response data
The normal response includes the function code, number of data bytes in the read block followed
by the register data (unless an exception occurs).
If 32-bit parameter addressing is used, then for each parameter read:
• Two 16-bit registers must be used in the request
• The register data in the response will contain 4 bytes of data
Example
To read drive parameters 0.20.021 to 0.20.023 (transaction ID = 42) with 32-bit data access and
standard addressing:
CT Parameter Addressing mode Protocol register
s.mm.ppp
Standard mm * 100 + ppp - 1
Modified mm * 256 + ppp - 1
Examples
16-bit 32-bit
Decimal Hex (0x) Decimal Hex (0x)
0.01.021
Standard 120 00 78 16504 40 78
Modified 276 01 14 16660 41 14
0.01.000
Standard 99 00 63 16483 40 63
Modified 255 00 FF 16639 40 FF
3.70.001
Standard 7000 1B 58 23384 5B 58
Modified N/A N/A N/A N/A
0.03.161
Standard N/A N/A N/A N/A
Modified 928 03 A0 17312 43 A0
Byte Description Byte Description
7 Function code 0x03 7 Function code 0x03
8
Start register address
(MSB)
8
Length of data in read block
(Bytes)
9
Start register address
(LSB)
9
Register data
(MSB)
10
Number of 16-bit registers
(MSB)
10
Register data
(LSB)
11
Number of 16-bit registers
(LSB)