Emerson E300 Series - Page 482

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CT MODBUS RTU Technical Data
482 E300 Design Guide
Issue Number: 1
If 32 bit parameter addressing is used, then for each parameter written:
• Two 16 bit registers must be used in the request
• Four bytes must be specified in the request
• The number of registers written in the response will be twice the
number of parameters written
Master request
Slave response
Example
Write the value 2000 to Pr 00.011 and 3000 to Pr 00.012 with 32 bit data
access
Master request
Slave response
FC23 - Read/Write multiple registers
This function code allows a contiguous series of registers to be written
and another contiguous series of registers to be read. The drive imposes
an upper limit on the number of registers to be written (16 in the case of
CSD100), and if this is exceeded the drive will issue an exception
response code 2.
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:
• For each parameter read or written, two 16 bit registers must be
used in the request
• For each parameter written, four bytes must be specified in the
request
• For each parameter read, four bytes of data will be used in the
response
It should be noted that the FC23 request is effectively an FC03 (read
multiple) request followed by an FC16 (write multiple) request. The write
is performed first and continues until any of the errors given for FC16
occur. Some parameters may have been written when an error is
detected, but no indication is given about how many parameters have
been written successfully. The read is always performed even if an error
is detected during writing. Any of the errors given for FC03 can occur
and the exception response is the same as for FC03.
Master request
Slave response
Example
Write the value 200 to Pr 00.054 and read Pr 00.057 with 32 bit data
access
Byte Description
0 Slave destination node address (1 – 247, 0 is global)
1 Function code 0x10
2 Start register address MSB
3 Start register address LSB
4 Number of 16 bit registers to write MSB
5 Number of 16 bit registers to write LSB
6 Length of register data to write (bytes)
7 Register data 0 MSB
8 Register data 0 LSB
7+byte count CRC LSB
8+byte count CRC MSB
Byte Description
0 Slave destination node address
1 Function code 0x10
2 Start register address MSB
3 Start register address LSB
4 Number of 16 bit registers written MSB
5 Number of 16 bit registers written LSB
6CRC LSB
7CRC MSB
Byte Value Description
0 0x01 Slave destination node address
1 0x10 Function code 0x10
20x40
Start register Pr 00.011
16384 + (100 x 0) + 11 – 1) = 16394 = 0x400A
30x0A
4 0x00 Number of 16 bit registers MSB
5 0x04 Number of 16 bit registers LSB
6 0x08 Length of register data to write (bytes)
7-10
0x00 0x00
0x07 0xD0
Register data 0
11-14
0x00 0x00
0x0B 0xB8
Register data 1
15 0x97 CRC LSB
16 0x85 CRC MSB
Byte Value Description
0 0x01 Slave destination node address
1 0x10 Function code 0x10
2 0x40 Start register address MSB
3 0x0A Start register address LSB
4 0x00 Number of 16 bit registers written MSB
5 0x04 Number of 16 bit registers written LSB
6 CRC LSB
7 CRC MSB
Byte Description
0 Slave destination node address (1 – 247, 0 is global)
1 Function code 0x17
2 Start register address to read MSB
3 Start register address to read LSB
4 Number of 16 bit registers to read MSB
5 Number of 16 bit registers to read LSB
6 Start register address to write MSB
7 Start register address o write LSB
8 Number of 16 bit registers to write MSB
9 Number of 16 bit registers to write LSB
10 Length of register data to write (bytes)
11 Register data 0 MSB
12 Register data 0 LSB
11+byte count CRC LSB
12+byte count CRC MSB
Byte Description
0 Slave destination node address
1 Function code 0x10
2 Length of register data in read block (bytes)
3 Register data 0 MSB
4 Register data 0 LSB
3+byte count CRC LSB
4+byte count CRC MSB