ADLINK PCI-C588/PCIe-C588/C584 - Manual (Page 45)

Expansion/Isolation Box User Guide
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Each port has two bit DIP switch to set for RS-232, RS-422 or RS-485
interface. In RS-485 mode, we had auto data direction function to maintain
no local echo condition, but user may still need to maintain just only one
port to output data, so RS-485 mode must be used in half-duplex
transmission environment. For full-duplex transmission environment, user
may need to use RS-422 mode.
In C584XB/C588XB box, we have one built-in switching power supply. This
power supply can accept 100-265VAC input or 48-60VDC input (option).
In C584XB box, we can use one DB37 to DB37 cable to connect with C584
card. In C588XB box, we can use one DB62 to DB62 cable to connect with
C588/C888. All the cable is connected in pin to pin direct connection type.
RS-422 interface application note:
RS-422 interface is used for point to point connection or multi-drop
application. We can use RTS & CTS signal to have hardware handshake
between two devices. But user may need to keep in mind that we can only
let one driver output signal to be active in one time, or you may let the driver
IC be burnt.
Even though we had put one 120 ohm terminator resistor in each input
signal pair, user may need to remove this terminator resistor for proper
operation.
Due to proper operation, user may not let one cable left in unconnected
condition. Because the crosstalk problem may let one transmit data signal
to be coupled to receive data i nput. This may lead wrong process in some
application environment.
Because RS-422 interface do not use DTR/DSR/DCD signal, user may not
use DTR/DSR handshake and DCD signal checking function in its
application, these signals are in inactive condition for R S-422 interface.
RS-485 interface application note:
RS-485 interface is used for multi -drop half-duplex application. Because we
had put auto-direction capability in the box, user may not use RTS signal to
control the data direction. So it is no use for RTS/CTS signal in RS-485
interface. Because we had put one 120 ohm terminator resistor in RXD
input signal pair, user may need to remove this terminator resistor for
proper operation.
Due to proper operation, user may not let one cable left in unconnected
condition. Because the crosstalk problem may let one transmit data signal
to be coupled to receive data input. This may lead wrong process in some
application environment.