Card Setup - SeaLevel ULTRA COMM+422.PCI User Manual

Card Setup

In all cases J1x is for port 1, J2x - port 2, J3x - port 3 and J4x – port 4.
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 ULTRA COMM+422.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 ULTRA COMM+422.PCI in an RS-485 application with existing
(i.e., standard RS-232) software drivers.
Headers J1B – J4B 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 – J4B 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 compatibility remove the jumpers at J1B – J4B.
Examples on the following pages describe all of the valid settings for J1B – J4B.
9
© Sealevel Systems, Inc. 7402 Manual | SL9063 7/2021