User manual

Connect Tech Xtreme/104 Plus, PCI-104 and PCI/104 Express Family User Manual
Revision 0.11
21
16 Electrical Interfaces Xtreme/104 Plus and Express
(RS-232/422/485 and RS-423 Models)
16.1 RS-232 Electrical Interface
This is the default setting for the interface selectable Xtreme/104-Plus and Xtreme/104-Plus
Opto. To operate a port in RS-232 mode, no jumpers are set on the corresponding jumper block.
16.2 RS-422/485 Electrical Interface
Xtreme/104 Express, Xtreme/104-Plus and Xtreme/104-Plus Opto RS-232/422/485 adapters
support three modes of RS-422/485 communication, as outlined below. (See Figure 8 to see
examples of jumper settings.)
16.2.1 Full Duplex 4-Wire Mode
In this mode, TxD+/- and RxD+/- are being driven to a known level all the time. This mode is
typically used in point-to-point situations much like RS-232. This is sometimes called RS-422
mode.
16.2.2 Half Duplex 2-Wire Mode
In Half Duplex 2-wire mode during transmission the TxD+/- line driver is enabled and the
RxD+/- is disabled. When the not transmitting, the TxD+/- is disabled and the RxD+/- is
enabled. The TxD+/- is disabled by tri-stating the output driver pins.
This mode is used in both point-to-point 2-wire connections and in multi-drop 2-wire bus type
connections. Special software setup is required so that the Xtreme/104 hardware automatically
performs the TxD and RxD enabled and disabling.
See the Driver Software Configuration section for software setup.
16.2.3 Multi-drop 4-Wire Mode
In this mode the TxD+/- line driver is enabled only when data is transmitted and RxD+/- is
enabled all of the time. This mode is used in multi-drop 4-wire connections. This mode is also
called “Multi-drop” slave.
See the Driver Software Configuration section for software setup.
16.2.4 Line Bias and Termination
The RS-422/485 transceivers, both transmit and receive can be optionally biased to produce a
line level mark condition through jumper selectable resistors. These options are typically used
in multi-drop 4-wire and 2-wire connections.
The RxD+/- features a combined Bias and Termination network.
The TxD+/- feature a single Termination resistor.
See the Jumper Block settings in the next section for more details.