Sealevel Systems, Incorporated. All rights reserved.
Introduction
Introduction
Overview
The Sealevel Systems ULTRA 485+2.PCI is a two channel PCI Bus serial I/O
adapter for the PC and compatibles and features the 16850 advanced UART. It
provides two field selectable RS-422/485 serial ports supporting data rates up to
460.8K bps. The 16850 advanced UART provides a 128 byte FIFO that helps
reduce processor overhead by reducing the number of interrupts that need
servicing. Each port can be individually configured.
Choose the RS-422 mode for long distance device connections up to 4000ft.
where noise immunity and high data integrity are essential. Select RS-485 and
capture data from multiple peripherals in a RS-485 multidrop network. Up to 31
RS-485 devices can be connected to each port to automate your data collection.
You can even mix the ports in any of the interface combinations to provide
maximum flexibility to your application.
In RS-422 mode, the card works seamlessly with the standard operating system
serial driver. In RS-485 mode, our special auto-enable feature allows the RS-485
ports to be viewed by the operating system as a COM: port. This allows the
standard COM: driver to be utilized for RS-485 communications. Our on-board
hardware automatically handles the RS-485 driver enable.
What’s Included
The ULTRA 485+2.PCI is shipped with the following items. If any of these
items are missing or damaged, contact the supplier.
• ULTRA 485+2.PCI Serial I/O Adapter
• Serial Utility Software
• User Manual
Factory Default Settings
The ULTRA 485+2.PCI factory default settings are as follows:
Port # Electrical Specification
Port 1 RS-422
Port 2 RS-422
To install the ULTRA 485+2.PCI using factory default settings, refer to
Installation on page 9.
For your reference, record installed ULTRA 485+2.PCI settings below:
Port # Electrical Specification
Port 1
Port 2
Sealevel Systems ULTRA 485+2.PCI Page 1
Card Setup
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 ULTRA 485+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 ULTRA 485+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 compatibility remove the jumpers at J1B and J2B.
Examples on the following pages describe all of the valid settings for J1B and
J2B.
Sealevel Systems ULTRA 485+2.PCI Page 2
Card Setup
Interface Mode Examples J1B – J2B
ATRTNE
Figure 1- Headers J1B and J2B, RS-422
ATRTNE
Figure 2 - Headers J1B and J2B, RS-485 ‘Auto’ Enabled, with ‘No Echo’
ATRTNE
Figure 3 - Headers J1B and J2B, RS-485 ‘Auto’ Enabled, with ‘Echo’
Sealevel Systems ULTRA 485+2.PCI Page 3
Card Setup
Interface Mode Examples J1B and J2B (continued)
ATRTNE
Figure 4 - Headers J1B and J2B, RS-485 ‘RTS’ Enabled, with ‘No Echo’
ATRTNE
Figure 5 - Headers J1B and J2B, RS-485 ‘RTS’ Enabled, with ‘Echo’
Address and IRQ selection
The ULTRA 485+2.PCI is automatically assigned I/O addresses and IRQs by
your motherboard BIOS. Only the I/O address may be modified by the user.
Adding or removing other hardware may change the assignment of I/O addresses
and IRQs.
Sealevel Systems ULTRA 485+2.PCI Page 4
Card Setup
Line Termination
Typically, each end of the RS-485 bus must have line terminating resistors
(RS-422 terminates at the receive end only). A 120-ohm resistor is across each
RS-422/485 input in addition to a 1K ohm pull-up/pull-down combination that
biases the receiver inputs. Headers J1A and J2A allow the user to customize this
interface to their specific requirements. Each jumper position corresponds to a
specific portion of the interface. If multiple ULTRA 485+2.PCI adapters are
configured in a RS-485 network, only the boards on each end should have
jumpers T, P & P ON. Refer to the following table for each position’s operation:
Name Function
P Adds or removes the 1K ohm pull-down resistor in the
RS-422/RS-485 receiver circuit (Receive data only).
P Adds or removes the 1K ohm pull-up resistor in the RS-422/RS-
485 receiver circuit (Receive data only).
T Adds or removes the 120 ohm termination.
L Connects the TX+ to RX+ for RS-485 two wire operation.
L Connects the TX- to RX- for RS-485 two wire operation.
P P T L L
Figure 6 - Headers J1A and J2A, Line Termination
Sealevel Systems ULTRA 485+2.PCI Page 5
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