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LTDVE4CH-20 | INSTRUCTIONS MANUAL
Function name
Function code
Note
Read Holding Registers
0x03
Write Single Register
0x06
Write Multiple Registers
0x10
Table 14: function codes supported by the controller
Any Modbus request containing an unimplemented function code is silently ignored by the controller
and no response, of any kind, is given back to the master. These supported function codes can be
used to access the controller internal register file, organized as an array of sixteen-bit (two bytes)
values. These function codes are briefly described in the following sections.
14.1.3. Read Holding Registers (0x03)
This function code is used to read the contents of a contiguous block of registers from the controller
register file. The master specifies the starting register address and the number of registers to be
read. Registers are addressed starting at zero. The register data in the response message are
packed as two bytes per register. For each register, the first byte contains the high order bits and the
second contains the low order bits.
14.1.4. Write Single Register (0x06)
This function code is used to write a single register in the controller register file. The master specifies
the address of the register to be written and the actual data to be written. Registers are addressed
starting at zero. The register data in the request message are packed as two bytes per register. For
each register, the first byte contains the high order bits and the second contains the low order bits.
The normal response is an echo of the request, returned after the register contents have been
written.
14.1.5. Write Multiple Registers (0x10)
This function code is used to write a block of contiguous registers (1 to 123 registers) in the controller
register file. The master specifies the starting register address, the number of registers and the actual
data to be written. Registers are addressed starting at zero. The register data in the request message
are packed as two bytes per register. For each register, the first byte contains the high order bits and
the second contains the low order bits. The normal response returns the function code, starting
address, and quantity of registers written.
14.2. Register file
Table 15: controller register file
summarizes all the Modbus registers implemented in the
controller. There are 512 registers, each of sixteen-bits (two bytes) in size. The registers are mapped
at contiguous addresses starting from 0 and ending to 511.
Address
Name
Type
Range
Description
0
DEVICE_TYPE
R
0-
65535
Device type
1
BOOT_VERSION
R
0-
65535
Bootloader firmware version
