Appendix c: rs 422/485 line interface, Blue heat/pci rs 422/485, Universal blue heat/pci rs 422/485 – Connect Tech Blue Heat/PCI PCI Serial Communications User Manual
Page 31: Appendix c: rs-422/485 line interface, Blue heat/pci rs-422/485, Full duplex mode, Half duplex mode, Multi-drop slave mode, Line bias/termination, Universal blue heat/pci rs-422/485
Blue Heat/PCI User’s Manual, Connect Tech Inc.
31
Revision
0.11
Appendix C: RS-422/485 Line Interface
For information on how to configure your RS-422/485 interface, find your specific Blue
Heat/PCI model below:
Blue Heat/PCI RS-422/485
You can order the Blue Heat/PCI RS-422/485 adapter with all ports RS-422/485 or a
combination of RS-422/485 and RS-232. The RS-422/485 electrical interface is a reliable high-
speed serial link that offers superior noise immunity and multi-drop network connectivity. The
RS-422/485 electrical interface is also a superset of the RS-422 electrical interface. The Blue
Heat/PCI RS-422/485 offers full RS-422/485 support in hardware. The modes are as follows:
Full Duplex Mode
In this mode, TxD & RxD are active all the time. This mode is typically used in point to point
situations much like RS-232.
Half Duplex Mode
In this mode the TxD line driver is enabled only when data is transmitted and 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.
Multi-drop Slave Mode
In this mode the TxD line driver is enabled only when data is transmitted and RxD is enabled all
the time. This mode is typically used in multi-drop "4 wire" connections.
Line Bias/Termination
On the Blue Heat/PCI RS-422/485 the RS-422/485 receivers are biased high through fixed
resistors. Please refer to
for a partial schematic.
Universal Blue Heat/PCI RS-422/485
Universal Blue Heat/PCI RS-422/485 adapters offer full RS-422/485 support in hardware like
the other Blue Heat/PCI RS-422/485 models. The modes include full duplex, half duplex, and
multi-drop slave. Universal Blue Heat/PCI RS-422/485 adapters offer the following additional
functionality:
Tri-state Control
Universal Blue Heat/PCI RS-422/485 adapters allow you to tri-state the line drivers on power
up. To tri-state the drivers on power up please ensure there is no jumper installed across the pins
on jumper block JI. Refer to
for the location of J1.
Line Bias/Termination
On the Universal Blue Heat/PCI RS-422/485 the RS-422/485 receivers are biased high through
fixed resistors. Please refer to
for a partial schematic.