Specifications

Technical Description
Sealevel Systems ULTRA 530.PCI Page 13
Technical Description
The Sealevel Systems ULTRA 530.PCI provides a PCI interface adapter with an additional asynchronous serial port
providing a versatile interface, field selectable as RS-232 for modems, printers and plotters, as well as
RS-422/485/530 for industrial automation and control applications.
The ULTRA 530.PCI utilizes the 16550 UART. This chip features programmable baud rates, data format, interrupt
control and a 16-byte input and output FIFO. Also available, as options, are the 16C650, 16C750 and 16C850
UART’s that provide deeper FIFO’s (32, 64, 128 bytes respectively).
One other unique feature of the ULTRA 530.PCI is the support for the Oxford Semiconductor 16C950. This chip
features a deep FIFO (128 bytes transmit and receive), automatic RS-485 driver enable, and the ability to receive a
clock for isochronous communications.
Isochronous Communications
Webster's New Collegiate Dictionary defines synchronous as "recurring or operating at exactly the same period."
The majority of the serial buses in use today operate asynchronously, that is, "not synchronous" or more literally, not
clocked. The same dictionary defines isochronous as "uniform in time; having equal duration; and recurring at
regular intervals." In this implementation of serial communications, isochronous is defined as asynchronous framing
(i.e. start, stop and parity bits) with the addition of a clock signal. This scheme allows for much higher data rates and
the use of digital lines (i.e. ISDN, T1) where a clock is supplied for data multiplexing.
Why is this exciting? Now, with a simple communications interface that responds to standard communication calls,
high-speed communications can be accomplished! For example: Company A wishes to send daily reports from the
London office to it’s New York office via an established satellite link. These links typically require a clock to
synchronize data. In the past, more expensive synchronous interface adapter and custom software would be required.
Now, utilizing the ULTRA 530.PCI interface adapter with the Oxford Semiconductor 16C950 UART, an off the
shelf product such as PROCOMM PLUS32 or Symantec’s PCANYWHERE32 can be utilized, at much higher data
rates than are possible via dialup services.
Connector Pin Assignments
RS-232 Signals
Signal Name Pin # Mode
GND Ground 7
RD Receive Data 3 Input
CTS Clear To Send 5 Input
DSR Data Set Ready 6 Input
TXC Transmit Clock 15 Input
RXC Receive Clock 17 Input
DCD Data Carrier. Detect 8 Input
RI Ring Indicator 22 Input
TD Transmit Data 2 Output
RTS Request to Send 4 Output
TSET Transmit Signal Element Timing 24 Output
DTR Data Terminal Ready 20 Output