Omega Vehicle Security OMG-ULTRACOMM2-PCI RS-232 - Manual (Page 6)

Card Setup
Omega Engineering OMG-ULTRA COMM+2.PCI Page 2
Card Setup
In all cases J1x refers to settings for the first port and J2x refer to settings for
the second port.
RS-485 Enable Modes
RS-485 is ideal for multi-drop or network environments. RS-485 requires a tri-state
driver that will allow the electrical presence of the driver to be removed 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 COMM+2.PCI 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 COMM+2.PCI
in a RS-485 application with existing (i.e. standard RS-232) software drivers.
Headers J1B and J2B are used to control the RS-485 mode functions for the driver
circuit. The selections are ‘RTS’ enable (silk-screen ‘RT’) or ‘Auto’ enable (silk-
screen ‘AT’). The ‘Auto’ enable feature automatically enables/disables the
RS-485 interface. The ‘RTS’ mode uses the ‘RTS’ modem control signal to
enable the RS-485 interface and provides backward compatibility with existing
software products.
Position 3 (silk-screen ‘NE’) of J1B and J2B is used to control the RS-485
enable/disable functions for the receiver circuit and determine the state of the
RS-422/485 driver. The RS-485 ‘Echo’ is the result of connecting the receiver
inputs to the transmitter outputs. Every time a character is transmitted; it is also
received. This can be beneficial if the software can handle echoing (i.e. using
received characters to throttle the transmitter) or it can confuse the system if the
software does not. To select the ‘No Echo’ mode select silk-screen position ‘NE’.
For RS-422/530/449 compatibility remove the jumpers at J1B and J2B.
Examples on the following pages describe all of the valid settings for J1B and
J2B.