Meilhaus Electronic ME-90 Series, Электронное руководство, Страница: 52 / 120

3.7 Operation Modes
Both the RS-232 and the RS-422/485 ports can be accessed like
standard COM ports under Windows. The RS-422/485 ports can
be used in the operation modes „RS-422“, „RS-485 half-duplex“
and „RS-485 full-duplex“. Each port of the board is configurable
independently. The configuration has to be done by the system
control (see chap. 2.3
Port Configuration. However, check the
transfer parameters in your application program (e.g. Hyper
Terminal).
Caution:
Never use more than one driver on an RS-422 bus, and in an RS-
485 system do not use an RS-422 driver. The electrical signals are
not compatible and may cause damage to the hardware.
3.7.1 The RS-232 Standard
The RS-232 interface used on the ME-9000/9100/9300 and ME-
90.
PC/104-Plus is an asynchronous serial standard interface e.g. for
data transfer between computers and terminals. A distinction is
drawn between DTE (Data Terminal Equipment) and DCE (Data
Communication Equipment). Terminals, printers and computers
belong to DTEs, modems belong to DCEs. The max. transfer rate
depends on the cable length and should not exceed 19,2 kBd for a
distance of 15 m.
The following signals are available:
TxD (Transmitted Data): This line carries serial data from the DTE
to the corresponding pin on the DCE. The line is held at a negative
voltage during periods of line idle.
RxD (Received Data): This line carries serial data from the DCE to
the corresponding pin on the DTE.
RTS (Request to Send): This line requests data from the DCE.
CTS (Clear to Send): When a half-duplex modem is receiving, the
DTE keeps RTS inhibited. When it becomes the DTE’s turn to
transmit, it advises the modem by asserting the RTS pin. When
the modem asserts the CTS, it informs the DTE that it is now safe