Omron NV3Q Series, Руководство по подключению

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Modbus Slave (RTU Mode)
Section 11-1
11-1 Modbus Slave (RTU Mode)
Overview of
Communications 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.
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.
PLC Model Selection • Select Modbus Slave (RTU Mode).
Applicable Devices
Communications Settings The following communications settings are recommended for the PT and PLC.
■
PT Communications Settings
*1 The NV3W does not have RS/CS control lines. Disable RS/CS flow control.
NV
PLC
RS-422A/485
Screen
Parts PT internal memory
(Modbus-RTU Master)
(Modbus-RTU Slave)
Reading/writing
internal memory
in the PT from
the master
Up to 31 PTs can be connected
Bit/word devices No. Comments
PT internal memory Bit devices Internal bits GR0 to GR255F
Word devices Internal bits WGR0 to WGR255
Data registers GDT0 to GDT2047
Holding registers GDT9080 to GDT9086 Internal clock data
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.
Item Setting
PT slave address 1 to 247
Baud rate 9,600 bps, 19,200 bps, 38,400 bps, 57,600 bps, 115,200 bps
Data length 8
Parity Odd, even, or none
RS/CS flow control
*1 Enabled (for NV4W or NV3Q)