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Xerox 7120 - Functional Description; Data Representation; EBCDIC Card Format; Binary Card Format

Xerox 7120
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2.
FUNCTIONAL
DESCRIPTION
DATA
REPRESENTATION
A
single
80-column
card
can
contain
data
in
either
of
two
formats:
EBCDIC
or
binary.
EBCDIC
CARD
FORMAT
In
the
EBCDIC
card
format
there
are
256
valid
punch
con-
figurations
for a
single
card
column (see
Appendix
A),
each
of
which
is
translated
into
an
8-bit
code
in
the
range
0-
2551Q(0016-FF16).
Thus,
the
EBCDIC
card
image
(i.e.,
the
80 columns of punch
configurations)
consists of a
trans-
lated
string
of
8-bit
bytes,
with
the
first
byte
of
the
string
corresponding
to
the
configuration
punched
in
column
1
and
the
last
byte
of
the
translated
string
corresponding
to
col-
umn 80
•.
The
card
image
is
always
presented
to
the
control-
ling system in column
order.
Figure 1
illustrates
how
the
first two columns of
an
EBCDIC
card
image
are
presented
to
the
controlling
system.
Note
that
column 2
contains
an
invalid
EBCDIC punch
configura-
tion,
which
is
translated
as 8 zeros
and
which
causes
a
trans-
mission
data
error
condition
(see
IErrorConditions"
in
Chapter
3).
If
column 1 of a
card
contains
punches in rows 1
and
2,
the
entire
card
is
interpreted
as
a
binary
card
image
rather
than
an
EBCDIC image (see IlRead
Orders"
in
Chapter
3).
II
)
000000000
1 2 3 4 5 6 1 8
tl
1111111111\
2122222222
3333333333
444444444
555555555
6666666~6
177171717
8888888888
Column
9999999999
J
123.;
5 6 1 B 910
~'
I
n
n+1
Byte
, " , ,
Data
11100
0001
1,0000
0000
I
Bit Position 0 1 2
314
5 6
710
1 2 3 i 4 5 6 7
Validity
Valid
Invalid
Figure 1. EBCDIC Read
Operation
2
Functional
Description
BINARY
CARD
FORMAT
In
the
binary
card
format
there
are
4096
possible punch
con-
figurations
for a
single
card
column,
and
all
configurations
are
valid.
In this format
each
card
column corresponds
toa
12-bit
code
in
the
range
0-4095
(00016-FFF16)'
with
each
row punch
corresponding
to
a 1 in
the
12-bit
code.
Thus,
the
binarycard
image consists
of
a string of
80
12-bitcodes,
with
the
first
code
corresponding
to
the
actual
punch
con-
figuration
in column 1 and
the
last
code
corresponding
to
the
actual
punch
configuration
in
column
80.
Because
Sigma
I/o
systems use
an
8-bit
byte
as
the
basic
data
group-
ing,
the
80
12-bit
codes
are
presented
to
the
controlling
system
as
120
8-b
i t
bytes.
Figure 2
illustrates
how
the
first two columns of a
binary
card
image
are
presented
to
the
controlling
system.
Note
that
for
odd-numbered
columns,
the
data
in
rows
12
through 5
comprise one
byte
and
that
the
data
in rows 6 through 9
are
combined
with
the
data
in rows
12
through
1 of
the
next
even-numbered
column
to
form a
second
byte.
A
third
byte
is
formed from
the
data
in rows 2
through
9 of the
even-
numbered
column.
Thus, for
each
odd-
even-numbered
pair
of
binary
card
columns,
the
controlling
system
receives
a
sequence
of
three
8-b
it
bytes.
Card
Row
IF
12
11
o 1 2 3 4
5.6
7 8 9
12
11
j 0
112
\
I
I
"-
I
...
I
Column
I
Byte
n
n+1
__
"""'.
___
,I
r""--
...
·---,
I f
I
0000000
12
J 4
567
1111111
2122222.
13333333,
414444444
155555555
61666666l
717777777
818888888
999999999
1 2 1
~
5 6 1 B
~
3.!56789
...
2
n+2
*
I
D.a
ta..
1 0 1 0 1 0 1 0 1 1 0 0
00 00
00
11
0 1 0 1 0 1 0 I
Bit
P
os
I
tI
on 0 I 2 3 4 5 6 7 0 I 2 3 4 5 6 7 0 I 2 3 I 4 5 6 7
Figure
2.
Binary Read
Operation
The
binary
card
image
is
always
presented
to the
controlling
system in column
order
and
in
the
byte
sequence
described
above.
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