11: M
ODBUS
C
OMMUNICATION
11-6 S
MART
AXIS P
RO
/L
ITE
U
SER
'
S
M
ANUAL
FT9Y-B1378
Function Code
The Modbus RTU of the SmartAXIS supports eight function codes as listed in the table below. Supported function codes and valid
slave addresses vary with each Modbus slave device to communicate with. Configure the function codes according to the
specifications of the Modbus slave devices.
Master Device Address
When function code 01, 02, 03, or 04 is selected to read data from Modbus slaves, designate the first data register or internal relay
number to store the data received from the Modbus slave. When function code 05, 06, 15, or 16 is selected to write data to
Modbus slaves, designate the first data register or internal relay number to store the data to write to the Modbus slave. Data
registers and internal relays can be designated as the master device address.
Data Size and Word/Bit
Designate the quantity of data to read or write. The valid data size depends on the function code. When function code 01, 02, 05,
or 15 is selected, designate the data size in bits. When function code 03, 04, 06, or 16 is selected, designate the data size in
words. For valid data sizes, see the table above.
Slave No.
Designate slave numbers 0 through 247. The same slave number can be designated repeatedly for different request numbers
which can be 1 through 255. In the Modbus communication, slave number 0 is used for a broadcast slave number. The broadcast
can be used to write the same data to all Modbus slaves.
Slave Address
Designate data memory addresses of Modbus slaves. The valid slave address range depends on the function code. For valid slave
addresses, see the table above. The allocations of memory addresses vary with each Modbus slave device. Refer to manuals for
each Modbus slave device.
Request Execution Device
To use request execution devices, click the radio button for “Use” and designate the first internal relay in the Modbus RTU Master
Request Table. Devices used for executing requests are automatically listed in the table. To execute a request, turn on the
corresponding request execution device.
Data registers can also be designated as the Request Execution Device. When the first data register is designated as the Request
Execution Device, data register bits as many as the number of requests are allocated from the least significant bit of the first data
register. Data register bits assigned as the execution relays are automatically listed in the Request Table.
When request execution devices are not designated, all requests programmed in the Request Table are executed continuously.
Error Status Data Register
To use error status data registers, click the radio button for “Use” and designate the first data register in the Modbus RTU Master
Request Table. Data registers used for storing error statuses are automatically listed in the table. When Use a single DR for all
communication requests is selected, the first data register is shared by all requests.
Function Code Data Size Slave Address SmartAXIS as Modbus Slave
01 Read Coil Status 1 to 128 bits 000001 - 065535
Reads bit device statuses of Q (output), R (shift register),
or M (internal relay).
02 Read Input Status 1 to 128 bits 100001 - 165535
Reads bit device statuses of I (input), T (timer contact), or
C (counter contact).
03 Read Holding Registers 1 to 64 words 400001 - 465535
Reads word device data of D (data register), T (timer
preset value), or C (counter preset value).
04 Read Input Registers 1 to 64 words 300001 - 365535
Reads word device data of T (timer current value) or C
(counter current value).
05 Force Single Coil 1 bit 000001 - 065535
Changes a bit device status of Q (output), R (shift
register), or M (internal relay).
06 Preset Single Register 1 word 400001 - 465535 Changes word device data of D (data register).
15 Force Multiple Coils 1 to 128 bits 000001 - 065535
Changes multiple bit device statuses of Q (output), R
(shift register), or M (internal relay).
16 Preset Multiple Registers 1 to 64 words 400001 - 465535 Changes multiple word device data of D (data register).
To Next Page
Loading...
Need help?
General
