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© Sealevel Systems, Inc. 3603 Manual | SL9111 7/2021
Technical Description
The PC-SIO-232 provides one RS-232 serial port utilizing the 16550 UART (Universal Asynchronous Receiver
Transmitter).
The PC-SIO-232 is addressable as any COM: port (e.g., COM1:, COM2:, etc.) The PC-SIO-232 provides for
selectable IRQs (3,4,5,7,9,10,11,12,15). I/O address and IRQ combinations are very flexible, and information
on selecting these combinations is available upon request. Please refer to the software available for the
PC-SIO-232 for any manual updates, corrections, and software specific changes.
Each COM: Port requires a minimum of one block of eight I/O addresses. For example, COM1: is usually
hex address 3F8. 3F8 is the base address, and the COM: ports extend through 3FF. In most applications,
each COM: port will utilize one IRQ.
If you have any questions concerning the Card and Socket Services Documentation and the software setup
of the PC-SIO-232,
please contact Sealevel System Technical support. Refer to
information.
Connector Pin Assignments for RS-232 (DB-25 and DB-9 Male)
Signal
Name
DB-25
DB-9*
Mode
GND
Ground
7
5
TD
Transmit Data
2
3
Output
RTS
Request To Send
4
7
Output
DTR
Data Terminal Ready
20
4
Output
RD
Receive Data
3
2
Input
CTS
Clear To Send
5
8
Input
DSR
Data Set Ready
6
6
Input
CD
Carrier Detect
8
1
Input
RI
Ring Indicator
22
9
Input
These assignments meet EIA/TIA/ANSI-574 DTE for DB-9 type connector.
Please terminate any control signals that are not going to be used. The most common way to do
this is connect RTS to CTS and RI. Also, connect DCD to DTR and DSR. Terminating these pins, if
not used, will help insure you get the best performance from your adapter.
