User Manual
© Sealevel Systems, Inc. 
- 8 - 
ACB-ULTRA.LPCI User Manual 
I/O Signal Derivation 
The ACB-ULTRA.LPCI input/output signals are directly generated via the Zilog 
16C32 IUSC. The following table defines these signals, their origin pin and signal 
name following the conventions set by the 16C32 user’s manual. If using a Sealevel 
Systems, Inc. supplied driver, this is for informational use only. 
Signal Source 
Transmit Data  16C32 TXD Pin 
Request To Send  16C32 Port7 Pin 
Data Terminal Ready  16C32 Port6 Pin 
Transmit Signal Element Timing  16C32 TXC Pin 
Receive Data  16C32 RXC Pin 
Clear To Send  16C32 CTS Pin 
Data Set Ready  16C32 RXREQ Pin 
Data Carrier Detect  16C32 DCD Pin 
Transmit Clock  16C32 TXCO Pin 
Receive Clock  16C32 RXCO Pin 
Ring Indicator  16C32 TXREQ Pin 
25 Pin Connector Signal Layouts (DB-25 Male) 
In all modes, Pin 1 has a 1K ohm resistor to GND and pin 25 has a 1K ohm resistor 
to +5V connection. This is useful for RS-485 biasing. If this presents a problem in 
your implementation, please contact Sealevel Systems’ Technical Support for aid in 
removing. 
RS-232 Signals 
Base+5, M3-M0=2, 0010 
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 
TM  Test Mode  25  Input 
RI  Ring Indicator  22  Input 
TXC  Transmit Clock  15  Input 
RXC  Receive Clock  17  Input 
TSET  Transmit Signal Element Timing  24  Output 
DTR  Data Terminal Ready  20  Output 
TD  Transmit Data  2  Output 
RTS  Request To Send  4  Output 
LL Local Loop-back  18  Output 
RL Remote Loop-back  21  Output 










