Modbus Slave (Rtu Mode) - Omron NV3Q Connection Manual

Modbus Slave (RTU Mode)

11-1 Modbus Slave (RTU Mode)

Overview of
Communications
PLC Model Selection
Applicable Devices
PT internal memory Bit devices
Word devices
Communications Settings
98
The PT is the Modbus-RTU slave.
Modbus-RTU commands are sent to the PT from the PLC or other Modbus-
RTU master to read and to write internal memory in the PT.
The parts on the screens of the PT read and write memory in the PT.
As a result, the parts on the screens of the PT read and write internal memory
in the PLC or other Modbus-RTU master indirectly through the internal mem-
ory of the PT.
Up to 31 PTs can be connected.
Reading/writing
internal memory
in the PT from
the master
Screen
Parts
Note The timing of reading/writing internal memory in the PT by the PT is not syn-
chronized with the timing of reading/writing internal memory in the PT from
the PLC. The data is updated in the master PLC after the communications
cycle in the master PLC.
Therefore, there can be delays between operations and displays on the PT
and reading/writing data in the PLC. Applications that require realtime read-
ing/writing of PT data are not possible.
• Select Modbus Slave (RTU Mode).
Bit/word devices
Internal bits
Internal bits
Data registers
Holding registers
Additional Information
GR or WGR addresses differ only in that they are for bits or words. They access
the same internal memory. For example, WGR1 specifies the 16 bits from GR10
to GR1F.
The following communications settings are recommended for the PT and PLC.
■
PT Communications Settings
Item
PT slave address
Baud rate
Data length
Parity
RS/CS flow control
*1 The NV3W does not have RS/CS control lines. Disable RS/CS flow control.
PLC
(Modbus-RTU Master)
RS-422A/485
Up to 31 PTs can be connected
PT internal memory
GR0 to GR255F
WGR0 to WGR255
GDT0 to GDT2047
GDT9080 to GDT9086
1 to 247
9,600 bps, 19,200 bps, 38,400 bps, 57,600 bps, 115,200 bps
8
Odd, even, or none
*1 Enabled (for NV4W or NV3Q)
Section 11-1
NV
(Modbus-RTU Slave)
No. Comments
Internal clock data
Setting