Emerson unidrive m300 - 7.2.7 Fc03 - Read Multiple Registers

SI-Ethernet User Guide 123
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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:
Master request data Slave response data
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)
Byte
Hex
value
Description Byte
Hex
value
Description
0-1 00 2A Transaction ID (42) 0-1 00 2A Transaction ID (42)
2-3 00 00 Protocol ID (0=TCP/IP) 2-3 00 00 Protocol ID (0=TCP/IP)
4-5 00 06 Length (Bytes=6) 4-5 00 0F Length (Bytes=15)
6 FF Unit identifier (FF= Drive) 6 FF Unit identifier (FF= Drive)
7 03 Function code (3) 7 03 Function code (3)
8-9 47 E4 Start register (20.20) 8 0C Data length (Bytes=12)
10-11 00 06 Number of registers (6) 9-12 ? Pr 0.20.021 data
13-16 ? Pr 0.20.022 data
17-20 ? Pr 0.20.023 data