User`s guide
Vector
ZCB
Single
Board
Cailputer
~.4.3
Asynchronous
serial
baud
rate
selection
You
select
the
desired
baud
rate
through
a
combination
of
hardware
switches
and
software.
If
you
are
using
the
standard
q:>erating
systems
and
Extended
Systens
Monitors
for
Vector
Graphic
Systens,
however, you need
only
be
concerned
with
the
hardware
switches.
The
hardware
switch
is
located
in
the
upper
left
hand
corner
of
the
board.
It
is
labeled
"Baud
Rate
Select".
The
switch
contains
eight
rockers
labeled
"I"
to
"8"
and
also
labeled
"9600,"
"4800,"
"2400," "1200,"
"600,"
"300,"
"150,"
and
"110."
The
switch
is,
in
addition,
labeled
"OPEN"
on
the
left
side
•.
To
select
one
of
the
labeled
baud
rates,
press
the
desired
rocker
down on
the
right
side,
i.e.
on
the
side
opposite
the
"OPEN"
designation.
Then
press
all
other
rockers
down
on
the
left
side,
i.e.
toward
the
"OPEN"
designation.
The
result
must
be
that
one
rocker
is
down
toward
the
right,
and
all
others
are
down
toward
the
left.
Otherwise
none
of
the
serial
channelS
will
not
\«)rk
at
all.
If
you
are
not
using
the
serial
channel,
switch
them
to
the
"OPEN"
J:X'Sition.
The
labeled
baud
rates
assume
that
the
corresponding
8251
will
be
initialized
for
a
clock
factor
of
16.
(It
creates
the
baud
rate
by
dividing
the
clock
input
by
16.)
This
initialization
is
handled
in
software,
as
described
in
the
8251
references
given
in
Perspective.
All
standard
Vector
Graphic
software,
unless
otherwise
dclcum::nted,
use
a
clock
factor
of
16,
and
therefore
the
labeled
baud
rates
are
correct.
However,
custon
software
can
use
a
clock
factor
of
64.
If
this
is
the
case,
the
actual
baud
rate
will
be
1/4
of
the
baud
rate
selected
on
the
switch.
(The
only
two
asynchroncus
clock
factors
allowed
by
the
8251'
s
are
16
and
64.)
Further,
it
may
be
desired
to
create
software
which
allows
the
operator
to
ch<x>se
between
two
baud
rates
that
differ
by a
factor
of
4.
For
example,
the
software
may
be
designed
in
conjunction
with
a
rrodem
that
can
accept
signals
at
either
300
or
1200
baud.
In
this
case,
you
would
create
the
software
so
that
the
operator's
input
determines
whether
the
8251
is
initialized
with
a
clock
rate
factor
of
64
or
16,
respectively.
Remember,
if
you
are
using
standard
Vector
Graphic
software,
do
not
\«)rry
about
this
software
option.
You
simply
set
the
baud
rate
for
a
desired
serial
channel
by
setting
the
baud
rate
select
switch
on
the
ZCB
II
board.
2.4.4
How
to
connect
nost
RS-232C
serial
terminals
and
printers
To
connect
the
serial
channel
to
an
external
peripheral,
plug
the
male
l6-pin
connector
of
the
ZCB
serial
I/O
cable
into
the
16-pin
socket
of
the
desired
serial
channel,
on
the
upper
right
side
of
the
board.
Then,
in
most
cases
connect
the
DB-25
socket
at
the
end
of
this
cable
to
the
peripheral,
using
a
25-wire
flat
ribbon
cable.
n=tails
(and
exceptions)
are
as
follows:
?ev.
l-B
6/11/80
2-11