Table of Contents
Advertisement
RS-232 TeChnical Information
When a DTE device such as another computer is connected
at the RS-232 port using the straight RS-232 cable, a
problem occurs.
A DTE-to-DTE communications link,
which is what the user must set up to attach the UNIX
PC directly to another computer, requires that the
transmit and receive signals and some of the control
signals be crossed.
This type of connection requires a
null modem cable.
The pins of concern are pins 2 and
3, which must be reversed on
~
of the connectors.
The following illustrations show two different pinouts
for null modem cables.
A null modem cable using the
pinout shown below works for terminal and UNIX-to-UNIX
(uucp) connections.
This null modem cable always
works, since no control leads are passed across the
interface; because of this, however, the line is not
disconnected when you turn off the terminal:
A
B
1
1-1 - - - - - - - - - - 1 1
1
7
1-1 - - - - - - - - - - 1 1
7
c:
C-3
Advertisement
Table of Contents
