HP AD278A and AD279A PCI Multiplexer Support Guide, November 2008

This cable is a three-wire null modem cable. Transmitted data on one end of the cable is connected
to Received data at the other end, and vice versa. The male DB-25 end can be plugged directly
into most serial terminals and printers without any adapters. The female DB-25 end plugs directly
into any RoHS DB-25 serial port.
DB-25 4-Wire Hardware Handshaking (DTR) Cable
The four-wire cable is sufficient for an older terminal, printer, or other DTE (Data Terminal
Equipment) devices configured for DTR (hardware) flow control. However, some terminals and
printers may use a signal other than DTR (Data Terminal Ready) for flow control. In addition,
some terminals and printers may have other cable requirements. Consult your terminal or printer
manual for this information. For more universal compatibility, use a fully-wired DB-25
terminal/printer cable.
Table B-3 lists the pin-out connection between the DB-25 adapter and the DB-25 terminal/printer
with DTR handshaking.
Table B-3 Terminal/Printer Cable with DTR Handshaking
DB-25 Male (Peripheral)DB-25 Female (Card End)
SignalPinPinSignal
RxD3Connected to2TxD
TxD2Connected to3RxD
DTR20Connected to5CTS
SG7Connected to7SG
GNDShellConnected (via
shield) to
ShellGND
RTS+CTS4+5Jumpered
IMPORTANT: Some terminal or printer manufacturers may use different methods of flow
control. Consult your documentation for specific wiring requirements.
DB-25 Hardware Handshaking (RTS/CTS) Cable
The cabling shown in Table B-4 is often sufficient for a terminal, printer, or other DTE devices
configured for RTS/CTS (hardware) flow control. However, some terminals and printers may
have other cable requirements. Consult your terminal or printer manual for this information.
For universal compatibility, use a fully-wired DB-25 terminal/printer cable.
Table B-4 lists the pin-out connection between the DB25 adapter and the DB-25 terminal/printer
with RTS/CTS handshaking.
Table B-4 Terminal/Printer Cable with RTS/CTS Handshaking
DB-25 Male (Peripheral)DB-25 Female (Card End)
SignalPinPinSignal
RxD3Connected to2TxD
TxD2Connected to3RxD
CTS5Connected to4RTS
RTS4Connected to5CTS
DTR20Connected to6+8DSR+DCD
SG7Connected to7SG
34 Peripheral Connections