Introduction
Parameter
x.00
Parameter
description format
Keypad and
display
Serial
communications
CT Modbus
RTU
PLC Ladder
programming
CTSoft
Parameter
x.00
Advanced parameter
descriptions
Commander SK Advanced User Guide 21
Issue Number: 9 www.controltechniques.com
The 2bit type field selects the data type according to the table below:
If a 32bit data type is selected then the slave uses two consecutive 16bit MODBUS registers (in 'big endian'). The master must also set the correct
'number of 16bit registers'.
Example, read Pr 20.21 through Pr 20.24 as 32bit parameters using FC03 from node 8:
Table 6-9 Master request
Table 6-10 Slave response
Reads when actual parameter type is different from selected
The slave will send the least significant word of a 32 bit parameter if that parameter is read as part of a 16 bit access.
The slave will sign extent the least significant word if a 16 bit parameter is accessed as a 32 bit parameter. The number of 16 bit registers must be
even during a 32 bit access.
Example, If Pr 20.21 is a 32 bit parameter with a value of 0x12345678, Pr 20.22 is a 16 bit parameter with a value of 0xABCD, and Pr 20.23 is a 16 bit
parameter with a value of 0x0123.
Type field
bits 15-14
Selected data
type
Comments
00 INT16 backward compatible
01 INT32
10 Float32
IEEE754 standard
Not supported on all slaves
11 Reserved
Byte Value Description
0 0x08 Slave destination node address
1 0x03 FC03 multiple read
20x47
Start register address Pr 20.21
(0x4000 + 2021 - 1) = 18404 = 0x47E4
30xE4
4 0x00 Number of 16bit registers to read
Pr 20.21 through Pr 20.24 is 4x32bit registers =
8x16bit registers
50x08
6 CRC LSB
7
CRC
MSB
Byte Value Description
0 0x08 Slave destination node address
1 0x03 FC03 multiple read
20x10
Length of data (bytes) = 4x32bit registers =
16bytes
3-6 Pr 20.21 data
7-10 Pr 20.22 data
11-14 Pr 20.23 data
15-18 Pr 20.24 data
19 CRC LSB
20 CRC MSB
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