IDEC FC6A-C16K1CE Communications Manual page 132

6: M C
ODBUS OMMUNICATION
Function Code
The Modbus RTU of the FC6A Series MicroSmart 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.
Function Code
01 Read Coil Status
02 Read Input Status
03 Read Holding Registers
04 Read Input Registers
05 Force Single Coil
06 Preset Single Register
15 Force Multiple Coils
16 Preset Multiple Registers
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.
6-6
Data Size
1 to 128 bits
1 to 128 bits
1 to 64 words
1 to 64 words
1 bit
1 word
1 to 128 bits
1 to 64 words
FC6A S M S A
ERIES ICRO MART
Slave Address
Reads bit device statuses of Q (output), R (shift register),
000001 - 065535
or M (internal relay).
Reads bit device statuses of I (input), T (timer contact), or
100001 - 165535
C (counter contact).
Reads word device data of D (data register), T (timer
400001 - 465535
preset value), or C (counter preset value).
Reads word device data of T (timer current value) or C
300001 - 365535
(counter current value).
Changes a bit device status of Q (output), R (shift
000001 - 065535
register), or M (internal relay).
400001 - 465535 Changes word device data of D (data register).
Changes multiple bit device statuses of Q (output), R
000001 - 065535
(shift register), or M (internal relay).
400001 - 465535 Changes multiple word device data of D (data register).
- -O T C
LL IN NE YPE OMMUNICATION
FC6A Series MicroSmart as Modbus Slave
M FC9Y-B1730
ANUAL