United Kingdom:One Omega Drive, River Bend Technology Centre
ISO 9002 CertifiedNorthbank, Irlam, Manchester
M44 5BD United Kingdom
TEL: +44 (0)161 777 6611FAX: +44 (0)161 777 6622
Toll Free in United Kingdom: 0800-488-488
e-mail: sales@omega.co.uk
OMEGAnet®Online Service Internet e-mail
www.omega.com info@omega.com
It is the policy of OMEGA to comply with all worldwide safety and EMC/EMI regulations that
apply. OMEGA is constantly pursuing certification of its products to the European New Approach
Directives. OMEGA will add the CE mark to every appropriate device upon certification.
The information contained in this document is believed to be correct, but OMEGA Engineering, Inc. accepts
no liability for any errors it contains, and reserves the right to alter specifications without notice.
WARNING: These products are not designed for use in, and should not be used for, patient-connected applications.
Figure 8 - Headers E8 and E9 RS-485 Mod e Enable........................................6
Figure 9 - Four Port RS-232/RS -422 Configuration Table...........................7
Figure 10 - Asynchronous Communications Bit Diagram..........................17
Introduction
Introduction
Overview
The OMG-ISO-COMM provides the PC with additional ground isolated serial
ports for terminals, modems, printers, etc. Isolation is important in installations
where the equipment being connected to the PC is either far from the PC, or on a
different power transformer circuit . Ground loop current is a commonly neglected
and misunderstood phenomena that leads to the failure (and destruction) of
communication interfaces. The OMG-ISO-COMM isolated boards provide up to
500 volts DC of isolation.
The OMG-ISO-COMM provides two or four DOS and Windows compatible
serial ports, and also offers extended ‘AT’ interrupts. Each port is independently
addressable as COM1: through COM4:, or any other I/O address up to 3FF Hex.
What’s Included
The OMG-ISO-COMM is shipped with the following items. If any of these items
are missing or damaged, contact the supplier.
• OMG-ISO-COMM Serial I/O Adapter
• Cable providing 2 DB-9 connectors.
• Software
Factory Default Settings
The OMG-ISO-COMM factory default settings are as follows:
Port # Base Address IRQ
Port 1 3F8 4
Port 2 2F8 3
Port 3 3E8 4
Port 4 2E8 3
For your reference, record installed OMG-ISO-COMM settings below:
Port # Base Address IRQ
Port 1
Port 2
Port 3
Port 4
OMG-ISO-COMMPage 1
Card Setup
Card Setup
The OMG-ISO-COMM contains several jumper straps which must be set for
proper operation.
Address Selection
Each port on the OMG-ISO-COMM occupies 8 consecutive I/O locations. A
DIP-switch is used to set the base address for these locations. Be careful when
selecting the base address as some selections conflict with existing ports. The
following table shows several examples that typically do not cause a conflict.
SW4 sets the I/O address for port 1, SW3 sets the address for port 2, SW2 sets
the address for port 3 and SW1 sets the address for port 4.
Address Binary Switch Position Setting
Hex A9 A0 1 2 3 4 5 6 7
280-287 1010000XXX Off On Off On On On On
2A0-2A7 1010100XXX Off On Off On Off On On
2E8-2EF 1011101XXX Off On Off Off Off On Off
2F8-2FF 1011111XXX Off On Off Off Off Off Off
3E8-3EF 1111101XXX Off Off Off Off Off On Off
300-307 1100000XXX Off Off On On On On On
328-32F 1100101XXX Off Off On On Off On Off
3F8-3FF 1111111XXX Off Off Off Off Off Off Off
Figure 1 - Address Selection Table
The following illustration shows the correlation between the DIP-switch setting
and the address bits used to determine the base address. In the example below,
address 300 is selected as a base. Address 300 in binary is XX11 0000 0XXX
where X = a non-selectable address bit.
A9A38E
ON
OFF
1 2 3 4 5 6 7
Figure 2 - DIP-Switch Illustration
Note: Setting the switch ‘On’ or ‘Closed’ corresponds to a ‘0’ in the address,
while leaving it ‘Off’ or ‘Open’ corresponds to a ‘1’.
Refer to Appendix A for common address contentions.
OMG-ISO-COMMPage 2
Card Setup
Port Enable / Disable
Each port on the OMG-ISO-COMM can be enabled or disabled with switch
position 8 on the DIP-switch. The port is enabled with the switch ‘On’ or
‘Closed’ and disabled when ‘Off’ or ‘Open’. If any port is disabled, be sure to
disable the interrupt request for that port by removing the IRQ jumper.
IRQ Selection
Headers E1, E2, E3 and E4 select the IRQ for each serial port. If COM1: is
selected, this jumper must be on the IRQ4 setting. If COM2: is selected, this
jumper must be on IRQ3.
Note: Most communications software applications default COM3: to IRQ4 and
COM4: to IRQ3. This requires the sharing of interrupts between COM1:
and COM3:, and between COM2: and COM4:. While this is the default, it
is not always the preferred setting. Check your software configuration
instructions to determine the most appropriate IRQ selection.
OMG-ISO-COMMPage 3
Card Setup
MSNMS
N
1
2
3
4
MSNMS
N
E5
3
4
Interrupt Mode Options
Header E5 selects the interrupt mode for each port. Each port must be set in the
correct mode to insure proper installation.
‘N’ indicates the (N)ormal, single interrupt per port mode. ‘S’ Indicates the
(S)hared interrupt mode, which allows more than one port to access a single IRQ.
Any two or more ports can share a common IRQ by placing the jumpers on the
same IRQ setting, and setting the appropriate selections at E5. Consult your
particular software for IRQ selection. If no interrupt is desired, remove the
jumper. ‘M’ indicates the inclusion of a 1K ohm pull-down resistor required on
one port when sharing interrupts.
E5
Figure 4 - Header E5, Normal IRQ Mode
Set jumpers to ‘S’ for shared interrupt mode on all blocks sharing an IRQ except
one. Set that port block for ‘M ’. This provides the pull-down resistor circuit that
makes sharing of IRQs possible. If you are using more than one OMG-ISO-COMM or a compatible card in a bus you should only have one port set to ‘M ’.
The following example shows all four ports sharing a single IRQ.
1 2
Figure 5 - Header E5, Shared IRQ Mode
OMG-ISO-COMMPage 4
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