Owner's manual
 Specifications 
Sealevel Systems SeaPORT+4 Page 8 
Technical Description 
The SeaPORT+4 utilizes four USB UARTs. These chips feature programmable 
baud rate, data format, 128 byte Dual Port TX Buffer, and 384 byte Dual Port 
RX Buffer. The RS-232/422/485 transceiver supports data rates up to 921.6K 
baud for RS-422/485 and 460.8K baud for RS-232. 
Features 
•  Hot pluggable device that does not require opening the case 
•  No system resources are required (i.e. I/O ports or IRQ’s) 
•  LED status indicators for USB Enabled and port activity 
Connector Pin Assignments 
RS-422/485  (DB 9 Male) 
Signal Name Pin # Mode 
GND Ground  5   
TX +  Transmit Data Positive  4  Output 
TX-  Transmit Data Negative  3  Output 
RTS+  Request To Send Positive  6  Output 
RTS-  Request To Send Negative  7  Output 
RX+  Receive Data Positive  1  Input 
RX-  Receive Data Negative  2  Input 
CTS+  Clear To Send Positive  9  Input 
CTS-  Clear To Send Negative  8  Input 
RS-232 (DB-9 Male) 
Signal Name  Pin # Mode 
GND Ground  5   
TX Transmit Data  3 Output 
RTS  Request To Send  7  Output 
DTR  Data Terminal Ready  4  Output 
RX Receive Data  2 Input 
CTS  Clear To Send  8  Input 
DSR  Data Set Ready  6  Input 
DCD  Data Carrier Detect  1  Input 
RI Ring Indicator  9 Input 










