SeaLevel IC485+ User manual

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
IC485+
User Manual | 1102

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Contents
CONTENTS...........................................................................................................................................................2
BEFORE YOU GET STARTED ...............................................................................................................................4
CARD SETUP ........................................................................................................................................................6
OPERATING SYSTEM INSTALLATION (FOR WINDOWS USERS)....................................................................10
TECHNICAL DESCRIPTION ...............................................................................................................................14
TECHNICAL SPECIFICATIONS..........................................................................................................................16
APPENDIX A –TROUBLESHOOTING................................................................................................................17
APPENDIX B –HOW TO GET ASSISTANCE .....................................................................................................18
APPENDIX C –ELECTRICAL INTERFACE ........................................................................................................19
APPENDIX D –ASYNCHRONOUS COMMUNICATIONS ..................................................................................20
APPENDIX E –SILK-SCREEN ............................................................................................................................21
APPENDIX F –COMPLIANCE NOTICES...........................................................................................................22
WARRANTY ........................................................................................................................................................23

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Introduction
The Sealevel Systems IC485+ is a single channel RS-232 to RS-422/485 asynchronous converter. It
provides one field selectable RS422/485 serial port supporting asynchronous data rates up to 115.2K bps.
The IC485+ is self-powered allowing it to correctly drive multi-drop RS-485 networks.
Configure the port as RS422 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 an RS485
multi-drop network. Up to 31 RS-485 devices can be connected to automate your data collection.
In RS-422 and RS-485 Auto modes, the card works seamlessly with the standard operating system serial
driver. Two additional methods are provided to control the communication line in RS-485 mode. The “Data
Enable” mode uses the transmitted data to enable the transmitter and requires no software drivers. This
mode has limitations that will be discussed in more detail later. The “RTS Enable” mode uses the UART
modem control signal RTS to control the communication line and requires the Sealevel Systems’ serial
driver.

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Before You Get Started
What’s Included
The IC485+ is shipped with the following items. If any of these items are missing or damaged, please
contact Sealevel for replacement.
•IC485+ Serial I/O Adapter
•Power Supply
Advisory Conventions
Warning
The highest level of importance used to stress a condition where damage could result to the
product, or the user could suffer serious injury.
Important
The middle level of importance used to highlight information that might not seem obvious or a
situation that could cause the product to fail.
Note
The lowest level of importance used to provide background information, additional tips, or other
non-critical facts that will not affect the use of the product.

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Factory Default Settings
The IC485+ factory default settings are as follows:
Port #
Electrical Specification
Port 1
RS-422
To install the IC485+ using factory default settings, refer to Installation.
For your reference, record installed IC485+ settings below:
Port #
Electrical Specification
Port 1

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Card Setup
RS-485 Enables 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.
DIP-switch SW1 is used to control the RS-485 mode functions for the driver circuit. The selections are:
‘RS-422 Mode’ (Always). This is the factory default mode that ensures the transmitter is always enabled.
This mode is intended for Full Duplex applications such as RS-422 or RS-485 4-wire Master mode where tri-
state control of the transmitter is not required.
‘RS-485 Auto Mode’. This mode uses an onboard MicroChip PIC microcontroller to sense the baud rate
and control the transmitter enable signal based on the detected baud rate. The logic assumes a minimum
baud rate of 1200bps and a word length of 10 bits (1 start bit, 8 data bits, and 1 stop bit). For baud rates of
38.4K or less, line turnaround should not exceed 4 bit times, 57.6K should not exceed 10 bit times, and
115.2K should not exceed 20 bit times after successfully autobauding.
‘RS-485 RTS Enable Mode’. The ‘RTS’ enable mode uses the ‘RTS’ modem control signal to enable the RS-
485 interface and provides backward compatibility with existing software products. Sealevel Systems’
serial driver should be used and configured for ‘RTS’ control providing a robust RS-485 solution.
‘RS-485 Data Enable Mode’. The ‘Data’ enable mode uses the transmit data stream to enable/disable the
transmitter. When the data bit is High (logic 1), the transmitter will be tri-stated and relies on the line biasing
resistors to place the line in the proper state. For this reason, line termination cannot be used thus reducing
the data rate and maximum cable length. This mode should only be used in applications that prevent the
use of the RS-485 Auto Mode or Sealevel Systems’ serial driver.

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Communication Mode Examples (Dip switch SW1)
Figure 1- Dip switch SW1, RS-422
Figure 2 –Dip switch SW1, RS-485 ‘Auto’ Enable
Figure 3 –Dip switch SW1, RS-485 ‘RTS’ Enable
Figure 4 –Dip switch SW1, RS-485 ‘Data’ Enable

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Line Termination and Receiver Echo Off/On
Typically, each end of the RS-485 bus must have a line-terminating resistor (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. DIP-switch SW2 allows customization of this interface
to specific requirements. Each DIP-switch position corresponds to a specific portion of the interface. If
multiple IC485+ adapters are configured in an RS-485 network, only the adapters on each end should have
DIP-switch SW2 position 1 on. One adapter should have DIP-switch SW2 positions 2 and 3 on. Refer to the
table below for each position’s operation.
DIP-switch SW2 position 6 is used to control the RS-485 enable/disable functions for the receiver circuit
and determines 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 enable the ‘No Echo’ mode DIP-switch SW2 position
6 should be on.
SW2
Function
1
Adds or removes the 120-ohm termination.
2
Adds or removes the 1K-ohm pull-up resistor in the RS-422/RS-485 receiver circuit (Receive data
only)
3
Adds or removes the 1K-ohm pull-down resistor in the RS-422/RS-485 receiver circuit (Receive
data only)
4
Connects TX+ to RX+ for RS-485 two-wire operation
5
Connects TX- to RX- for RS-485 two-wire operation
6
Receiver Echo Off/On (On = Echo Off)
Figure 5 –Dip switch SW2, Line Termination and Echo Off/On

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Electrical Interface Examples (DIP switch SW2)
Figure 6 –RS-422 with Termination and Receiver Echo
Figure 7 –RS-485 2-wire with Termination and Receiver No Echo
Figure 8 –RS-485 2-wire no Termination and Receiver No Echo

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© Sealevel Systems, Inc. 1102 Manual | SL9135 6/2021
Operating System Installation (For Windows Users)
RS-422/RS-485 Four-Wire Master/RS-485 Two-Wire Auto Mode Installation
If your application is 4-wire Full Duplex RS-422 or 4-Wire RS-485 Master, where control of the transmitter is
not required, or 2-wire RS-485 and you intend to use the Auto Mode to control the transmitter, simply
connect the IC485+ to an existing RS-232 COM: port. This will utilize the Operating System Serial Driver to
control the COM: port. You will want to install Sealevel’s diagnostic utility, WinSSD, to test and verify proper
operation of the port.
Begin by locating, selecting, and installing the correct software from the Sealevel software driver database.
Choose Asynchronous COM: Port Software, SeaCOM. Continue with the installation until the “Setup Type”
dialog, as shown below, appears. Choose “WinSSD Utility” to install just the diagnostic tool. A Start Menu
Program Group, “SeaCOM” will be created and WinSSD can be started from there.
RS-485 Two-Wire and RS-485 Four-Wire Slave Installation
If your application is 2-wire Half-Duplex RS-485 or 4-Wire Full-Duplex RS-485 Slave that requires control of
the transmitter, the IC485+ provides 3 methods of control.
The first method is ‘Auto Enable’ which uses an onboard microcontroller to sense the baud rate and control
the transmitter enable. This mode assumes a minimum baud rate of 1200bps and a word length of 10 bits.
This would be the preferred method, as it requires no software in order to work. This mode should be used
with line termination since the transmitter is driving the line during transmission.