The tenus Data Communication
Equipment and Data Tenuinal
Equipment
derive
from
the
original
purpose
for RS-232C
- to connect
a terminal
with
a
communication
device
such
as a modem.
A computer
does
not
have
to be
involved
at all.
Since a computer can either play the part of a terminal,
when
connected
to a modem,
or
it can
play
the
part
of
communication
equipment,
when connected
to a terminal, a computer
serial
channel
can
be
used
either
as DeE or DTE.
However,
a given
serial
channel can only be
wired up as one or the other at anyone
time.
If the channel happens
to be
wired up to look like CCE, and you want to connect it to another CCE such as
a rrodem, then the RS-232C
connection
will
not
wo rk.
Both
ends
would
be
transmi tting on the same lines and receiving on the same lines.
Before tI1e
RS-232C connection
can be made, in this case, you must rewire the computer's
serial
channel
so that it receives and transnits on the lines specified
for
I1I'E.
The
Bitstreamer
II Board
is shipped with one RS-232C Serial I/O Cable.
To enable one of the serial channels
to communicate
over
an RS-232C
line,
you will
connect
one
end
of this
line
to one of the three serial channel
sockets on the board, and the other end, having
an RS-232C
standard
DB-25
female
connector,
to the back panel of the computer.
The cable
is designed
so that appropriate
signals from the board are directed
to the RS-232C lines
at the D8-25
connector
as if it were Data Communications
Equipment.
Thus,
the resulting 08-25 socket
at the
rear
of the computer
is a DCE
RS-232C
~.
channel.
I
Additional
8itstreamer
II Serial
I/O Cables
are
available
from Vector
Graphic
for the second and third serial channels on the board.
Drivers are provided
for each serial channel to enable the 8251 Transmit
Data
and
Receive
Data
lines
to input or output at RS-232C voltage levels.
These receivers and drivers are already connected on the board, requiring no
jumpering.
When a serial I/O cable is installed for a given serial channel,
these signals are connected
to RS-232C lines 3 and 2 respectively.
In addition,
for each of the 825l's, three of ~~e RS-232C control lines
are pulled up to +12V
(lines 5,
6,
and 8).
This is the ON state in RS-232C.
(Normally,
this will ENABLE equipment that requires such a signal.)
When a
serial
I/O cable
is installed
for a given
channel,
these
signals
are
available on the cable's 06-25.
These signals are always ON if the board is
used
without
modification.
However,
you can install jumpers and RS-232C
line drivers to enable the 8251 to dynamically
control any
t'NO of
them
via
software.
Summary of Contents for Bitstreamer II
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