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IBM Series 1 - Page 17

IBM Series 1
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timing
condition.
(Timeout
conditions
for
error
detection
are,
of
course,
not
excluded.)
An
asynchronous
channel
allows
the
attachment
of
devices
that
have
various
speeds
and
technologies
over
a
wide
range
of
distances
or
delays.
All
of
the
I/O
channel
signal
lines
are
TTL
level
compatible.
This
allows
the
user
to
attach
a
wide
variety
of
I/O
devices.
The
I/O
channel
signal
lines
are
distributed
internally
through
the
processor
backpanel
board
to
each
I/O
attachment
card
socket.
Distribution
of
the
channel
signal
lines
can
be
continued
by
connecting
cables
or
a
channel
repower
feature
from
a
processor
I/O
socket
(usually
the
A-socket)
to
an
adjacent
I/O
expansion
unit
as
the
particular
processor
or
configuration
requires.
A
channel
repower
feature
card
is
required
if
the
channel
is
extended
from
an
1/0
expansion
unit
to
an
additional
I/O
expansion
unit.
IBM
I/O
attachment
cards
plug
directly
into
the
backpanel
sockets.
External
I/O
devices
are
connected
to
the
attachment
cards
via
top-card
connectors.
Two
features
are
available
for
connecting
non-IBM
devices
directly
to
the
channel:
(1)
the
channel
socket
adapter
feature
and
(2)
the
channel
repower
featur~.
•
Channel
socket
adapter
feature
--
this
feature
consists
of
an
IBM
printed
circuit
card
that
plugs
into
the
backpanel
of
the
processor
unit
or
I/O
expansion
unit.
An
industry
standard
connector
on
the
top
edge
of
the
IBM
printed
circuit
card
accepts
the
userts
I/O
adapter
card.
For
further
information,
see
"Socket
Adapter
Featu['e"
near
the
end
of
this
chapter.
•
Channel
repower
feature
--
this
feature
is
a
logic
card
that
repowers
and
isolates
the
channel
signal
lines.
This
card
can
be
installed
in
any
I/O
socket,
as
the
last
series
element
on
the
channel,
to
provide
for
connection
of
additional
I/O
adapters
or
controllers.
For
further
information,
see
"Channel
Repower
Feature"
near
the
end
of
this
chapter.
If
the
user
connects
directly
to
the
channel
at
the
backpanel
sockets
instead
of
through
one
of
the
available
features,
unit
load,
power,
and
physical
requirements
must
be
considered.
These
and
other
requirements
are
discussed
in
subsequent
sections
of
this
chapter.
2-2
GA34-0033
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