board, right next to the corresponding pads in Areas H, I, or
J
(dependin;
on which channel you are concerned with).
If you
.A..Q.E
using a Null Modem Cable, the +12
VDC
signals
are
routed
to
RS-232C
lines
4, 20, and 19 respectively, on M1ich the Data Communications
Equipment
c.~\j
r12 VDC without harm.
Therefore,
\vhen using
a Null
Modem
Cable,
you do not have
to disconnect a line from +12 VDC unless you
want to control the status of that line from software.
To control
an RS-232C handshaking line from software, it must pass from
an 8251 output pin to the input of one of L~e driver circuits in a 1488 quad
line driver.
It must then pass from ~~e output of this 1488 driver circuit
to the RS-232C
line,
(using one
ot
the
pads
in Area
H,
I,
or
J,
if
possible. )
To respond to an incoming RS-232C handshaking
line,
it must
pass
(from
one of the pads in Area H, I, or
J,
if possible) to the input of one of the
receiver circuits in a 1489 quad line receiver.
It must then pass from
the
output
of this 1489
receiver circuit to one of the 8251 input pins, (using
one of the pads in Area N,
0,
or
Pl.
1488
=
a quad line driver.
1489
=
a quad line receiver.
There is one spare receiver circuit and one spare driver
circuit
on
the
board.
The RS-232C input to the spare receiver is U26 pin 1 and its output
is U26 pin 3.
The input to
t..he
spare driver is U22 pin
2 and
its RS-232C
output
is
U22 pin
3.
Wire
your
jumpers
directly
to these
pins,
when
required.
If additional
receiver and/or driver circuits are required, they can be
added to the board, using
the two spare
sockets
U25
and U28.
Note
that
these
are 16-pin
sockets, though a 1488 and 1489 are 14 pin chips.
Insert
~~e chip with its notch upward in the TOP 14 holes in the socket.
It does
not matter
which
of the two spare sockets is used for a 1488 and which is
used for a 1489.
Both a 1488 and a 1489 have four circuits
in each,
which
should
be more
than enough to handle all required handshaking for at least
one channel.
Next to socket U25 there are two jumper areas, Area C and Area
D.
Next
to socket
U28 there are two more jumper areas, Area
E:
and Area F.
Use a pad in one of the jumper areas rather than jumpering
directly
to the
sockets.
Summary of Contents for Bitstreamer II
Page 1: ...lit t tiCAli1iC I JI U E I mAnUAL...
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Page 3: ...BITSTREAMER II BOARD Revision 1 USER S MANUAL Revision A January 1 1980...
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