Omega Vehicle Security ISA RS-422 - Manual (Page 9)

Card Setup
OMG-ULTRA-SIO Page 5
Set the jumper to ‘S’ if you are using more than one OMG-ULTRA-SIO in a bus
or to completely remove the pull-down resistor for hardware compatibility.
Setting the adapter in this configuration when it is not accompanied by a pull-
down resistor will prevent the ports from triggering an interrupt.
1
2
N S M
E5
E6
Figure 5 - Header E5 & E6, Sharing IRQs with another adapter
RS-485 Enable Modes
RS-485 is ideal for multi-drop or network environments. RS-485 requires a tri-state
driver (not dual-state) that will allow the electrical presence of the driver to be
remo ved from the line. The driver is in a tri-state or high impedance condition
when this occurs. Only one driver may be active at a time and the other driver(s)
must be tri-stated. The output modem control signal Request To Send (RTS) is
typically used to control the state of the driver. Some communication software
packages refer to RS-485 as RTS enable or RTS block mode transfer.
One of the unique features of the OMG-ULTRA-SIO is the ability to be RS-485
compatible without the need for special software or drivers. This ability is
especially useful in Windows, Windows NT, and OS/2 environments where the
lower level I/O control is abstracted from the application program. This ability
means that the user can effectively use the OMG-ULTRA-SIO in a RS-485
application with existing (i.e. standard RS-232) software drivers.