Impulse 1103 - Manual (Page 11)

Technical Description
Sealevel Systems IC485+I Page 9
Technical Description
The Sealevel Systems IC485+I converts an existing RS-232 serial port into an isolated, field selectable, RS-422/485
port for industrial automation and control applications. 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 phenomenon that leads to data loss and the destruction of
communications interfaces.
Connector Pin Assignments
RS-232 Signals (DB-25 Female)
Signal Name Pin # Mode
GND Ground 7
RD Receive Data 3 Input
CTS Clear To Send 5 Input
DSR Data Set Ready 6 Input
DCD Data Carrier. Detect 8 Input
RI Ring Indicator 22 Input
TD Transmit Data 2 Output
RTS Request to Send 4 Output
DTR Data Terminal Ready 20 Output
Note: These assignments meet EIA/TIA/ANSI-232E DTE
Technical Note: The modem control signals are biased in the following fashion: RTS and CTS are connected,
DTR is connected to DCD and DSR, and RI is tied inactive.
RS-422/485 Pin Assignments (6 Position Screw Terminal)
Signal Name Pin # Mode
RDB RX+ Receive Data Positive 1 Input
RDA RX- Receive Data Negative 2 Input
TDB TX+ Transmit Data Positive 3 Output
TDA TX- Transmit Data Negative 4 Output
GND GND Ground 5
SHIELD SH Shield 6