Hitachi HX-RIO3 Series User Manual page 30

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3(0x03) Read Holding
Registers
(Read output
word)
4(0x04) Read Input
Registers
(Read input word)
5(0x05) Write Single Coil
(Write one-bit
output)
6(0x06) Write Single
Register
(Write one-word
output)
8(0x08) Diagnostics
(Read diagnostic
register)
*Refer to the
6.2.1
15(0x0F) Write Multiple
Coils
(Write a number
of
output bits)
16(0x10) Write Multiple
registers
(Write a number
of
output words)
23(0x17) Read/Write
Multiple registers
(Read a number
of
input words
/Write a number
of
output words)
- Refer to MODBUS APPLICATION PROTOCOL SPECIFICATION V1.1a
This function code is used to read the contents of a contiguous block of
holding registers in a remote device. The Request PDU specifies the
starting register address and the number of registers. The register data in
the response message are packed as two bytes per register, with the binary
contents right justified within each byte. For each register, the first byte
contains the high order bits and the second contains the low order bits.
This function code is used to read from 1 to approx. 125 contiguous input
registers in a remote device. The Request PDU specifies the starting
register address and the number of registers. The register data in the
response message are packed as two bytes per register, with the binary
contents right justified within each byte. For each register, the first byte
contains the high order bits and the second contains the low order bits.
This function code is used to write a single output to either ON or OFF in a
remote device. The requested ON/OFF state is specified by a constant in
the request data field. A value of FF 00 hex requests the output to be ON. A
value of 00 00 requests it to be OFF. All other values are illegal and will not
affect the output.
This function code is used to write a single holding register in a remote
device. Therefore, register numbered 1 is addressed as 0. The normal
response is an echo of the request, returned after the register contents have
been written.
MODBUS function code 08 provides a series of tests for checking the
communication system between a client ( Master) device and a server
( Slave), or for checking various internal error conditions within a server. The
function uses a two–byte sub-function code field in the query to define the
type of test to be performed. The server echoes both the function code and
subfunction code in a normal response. Some of the diagnostics cause data
to be returned from the remote device in the data field of a normal response.
This function code is used to force each coil in a sequence of coils to either
ON or OFF in a remote device. The Request PDU specifies the coil
references to be forced. Coils are addressed starting at zero. A logical '1' in
a bit position of the field requests the corresponding output to be ON. A
logical '0' requests it to be OFF. The normal response returns the function
code, starting address, and quantity of coils forced.
This function code is used to write a block of contiguous registers (1 to
approx. 120 registers) in a remote device. The requested written values are
specified in the request data field. Data is packed as two bytes per register.
The normal response returns the function code, starting address, and
quantity of registers written.
Read a number of input words /Write a number of output words This function
code performs a combination of one read operation, and one write operation
in a single MODBUS transaction. The write operation is performed before
the read. The request specifies the starting address and number of holding
registers to be read as well as the starting address, number of holding
registers, and the data to be written. The byte count specifies the
number of bytes to follow in the write data field. The normal response
contains the data from the group of registers that were read. The byte count
field specifies the quantity of bytes to follow in the read data field.
HX-RIO3 Series