Vector Graphic Bitstreamer II User Manual - page 23
The 8itstreamer
II has
two independent parallel input/output
channels,
called Parallel Channels
A and 8.
Each
channel
has
its own
34-pin
edge
connector.
Vector
Graphic
supplies
an optional 34-lina ribbon cable that
connects
to this
edge
connector.
The
other
end of this
cable
has
no
connector
on it, allowing
you to configure it as desired.
Many of the 34
lines are not used, as discussed below.
Each parallel channel has eight pins for output and eight pins for input.
Additional
pins
provide
+5 VOC,
+12 VOC,
-12 VOC,
and GND.
Exact
pin
assignments
are given
in Table
12 in Section
2.8.
Input
and output is
accomplished using IN and
OlJI'
machine language instructions wi thin sof twa re
prepared for specific applications.
Output is latched on the board, so that
after
an OUT
instruction
is executed,
the eight
bits
of
data
remain
available
to the external
device
until the computer changes it.
Input is
NOT latched, so that software must be \vritten to sense in some way that data
is available and to input that data.
There are no interrupt lines connected
to the parallel channels.
Table 2 gives the specific machine
language
I/O
addresses assigned to each parallel channel.
We repeat a points made earlier:
as sources of interrupts, you cannot
A for normal parallel output.
It is
register.
If you are using the 825ls on the board
use the output side of Parallel Channel
used instead as the interrupt
masking