ICS ELECTRONICS 9099, Инструкция по эксплуатации, Страница: 53 / 178

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3.2.8 Operation from the USb bus (9009 Only)
The 9009's USB interface is fully IEEE-488.2 compatible and responds to all
of the IEEE-488.2 Common Commands. The USB Interface has access to
all of the 9009's SCPI and Modbus commands and to the its Status Reporting
Structure. Service Requests are not sent over the USB bus so the user has to
query the Status and ESR Registers to check for errors. The handling of the
Modbus slave device is the same as described in paragraph 3.2.2.
3.2.9 Modbus Serial Communication
The 9099's communication path to the Modbus RTU slave device is serial and
requires that the user set the 9099 and the Modbus slave device to the same
serial settings. Each Modbus device has its own address so that it can identify
and respond to serial packets sent to its address. Although the typical Tem-
perature Chamber or Process has only one Modbus Controller, the 9099 can
drive multiple Modbus devices on an RS-485 network.
The 9099 uses a combination of internal jumpers and an RS-485 Enable setting
to enable RS-232, RS-485 four-wire or RS-485 two-wire communication. The
9099 has an internal RS-485 termination network that can be switched onto
the RX signal pair to maintain the RS-485 lines in the mark state when they
are not being driven.