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IBM Series 1 - Page 18

IBM Series 1
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c
(;
o
FUNCTIONAL
DESCRIPTION
OF
THE
I/O
CHANNEL
SIGNAL
LINES
The
I/O
channel
consists
of
81
signal
lines.
These
signal
lines
are
divided
into
two
physical
groups:
(1)
the
.§~llic~
g£Q~
and
(2)
the
Eol!
g£QYE.
Eaen
group
can
operate
concurrently
and
asynchronously
with
the
other
group.
However,
the
initiation
of
sequences
on
the
channel
is
interdependent.
The
service
group
supports:
•
Data
and
control
information
transfers
•
1PL
initiation
•
Reset
functions
The
poll
group
supports:
•
Cycle
steal
requests
from
the
devices
•
Interrupt
requests
from
the
devices
•
Acknovlegement
of
both
types
of
requests
The
I/O
channel
signal
lines
are
listed
by
group
in
Figures
2-1
and
2-2.
!Q!~.
The
direction
shown
for
each
line
assumes
that
the
I/O
channel
originates
on
the
left;
I/O
attachments
are
on
the
right.
The
signal
lines
associated
with
the
service
group
are
listed
in
Figure
2-1.
Processor
I/O
Channel
2-3

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