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The PCI-ICM-1S is a single port asynchronous optically isolated serial
communication card that can be installed in any 3.3V or 5V PCI slot
computer. Data lines are opto-isolated from the computer and from each
other to assure communication even when large common mode voltages and
noise are imposed.
The card supports RS-422 and RS-485 balanced-mode
transmission/reception. Each card has capability to add bias voltage.
(RS-485 communication requires that one transmitter in the network must
supply a bias voltage to ensure a known “zero” state when all
transmitters are OFF). Also, receiver inputs at each end of the network
should be terminated to eliminate ringing. The card supports these
options by means of jumpers on the card.
Type 16550 UARTs are used as the asynchronous communication
elements. These include a 16-byte transmit/receive FIFO buffer to
protect against lost data in multi-tasking systems while maintaining
100 percent compatibility with the original IBM serial port.
A crystal oscillator is located on the card and permits precise
baud rate capability up to 115,200 baud. Higher baud rates, up to
460,800 baud, are achieved by changing a jumper on the card. The
driver/receivers used, type 75176, are capable of driving extremely
long communication lines at high baud rates. They can drive up to
±60
mA on balanced lines and receive inputs as low as 200 mV differential
signal superimposed on common mode noise of +12V to -7V. In case of
communication conflict, the driver/receivers feature thermal shutdown.
When the card is first installed, the operating system will
detect it as new hardware and assign it an IRQ number and base address.
There are no switches to set or base addresses to assign, making it
easy to use. From this point on, the card behaves as a standard COM
port.
Features
- Universal PCI, PCI-X, 3.3V and 5V compatible
- Optically isolated, asynchronous serial communications
- Supports RS-422 and RS-485 protocols
- Automatic control of RS-485 driver under all operating systems
- Includes type 16550 UART with 16-byte FIFO buffers
- Baud rates up to 460,800 baud
- Detected as standard COM port by all operating systems
- No base address or IRQ switches to set
RTS AND AUTO
TRANSCEIVER CONTROL
In RS-485 communications the driver must be enabled
when needed and
then disabled to permit all cards on the network to share a two-wire or
four-wire cable. The card has two methods to control the driver:
automatic (AUTO) and request-to-send (RTS) control. Under automatic
control, the driver is enabled (and the receiver disabled) when data
are ready to be transmitted. When transmission is complete, the driver
remains enabled for the transmission time of one additional character
and then is disabled. The card automatically adjusts its timing to the
baud rate of the data. (NOTE: For use in half-duplex mode under
Windows, the cards must be operated in the AUTO mode.) In the RTS mode,
application software must set a bit to enable the driver and reset that
bit to disable the driver.
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