User manual

Connect Tech Xtreme/104 Plus, PCI-104 and PCI/104 Express Family User Manual
Revision 0.11
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18.3 Line Modes XIG 12 Port Opto
18.3.1 Low Power Shutdown
This mode has been removed from Rev C models. It was found to not provide a significant
power savings due to the low efficiency of DC-DC converters at low loading. The “Slow Slew
Rate” feature was added in Rev C models, see below. Rev C models have other design
improvements which should provide lower power consumption overall.
18.3.2 Slow Slew Rate (Rev C models)
The slow slew rate feature of the RS232/485 transceiver has been added in place of the low power
shutdown. This feature applies to both RS232 and RS485 and will limit the output baud rate to
250kpbs. The benefits of this are:
 Power Savings
 Reduced EMI
 Ability to operate RS485/422 networks without termination resistors (thus conserving
more power).
18.3.3 RS-232 Electrical Interface
Standard RS-232 mode.
18.3.4 Full Duplex 4-Wire RS485
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, where long distances are required.
18.3.5 Multi-drop 4-WireRS485
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 typically used in multi-drop 4-wire connections.
See the Driver Software Configuration section for software setup.
18.3.6 Half Duplex 2-Wire RS485
In Half Duplex mode the TxD+/- line driver is enabled only when data is transmitted, whereas,
the RxD+/- is disabled when data is being transmitted. This mode is typically used in either
point-to-point 2-wire connections or in multi-drop 2-wire bus connections.
See the Driver Software Configuration section for software setup.
18.3.7 Line Bias/Termination
The RS-422/485 transceivers, both transmit and receive are optionally biased and terminated to
produce a stable idle condition through jumper selectable resistors.