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Paper Tape Reader
The paper tape
reader
will read 5-, 6-, 7-, or 8-level tape under program control, or 8-level
tape under hardware control.
When reading is done under hardware control, this is referred
to as
"
hardware load." Normally, 8-level tape is used in both cases.
The reader is permanently tied to buffer selector address 0.
It
operates like any other remote
terminal connected to the buffer selector when under program control, in the sense that it uses
the external function drivers for control and the external status lines for testing. As information
is read,
it
is transferred into input buffer 0 and the receive flag is set to indicate that data is
present. This flag may
be
tested by an NES command.
The primary function of the paper tape reader is to contain either a bootstrap program to be
used
at
the start of
a
day, or a special restart and error recovery program to be used in the
event that
an
error
condition
develops in the execution of the normal program.
The secondary function of Hardware Load and the paper tape reader is to initially load the
programs into memory.
Once the programs
are
loaded,
.
they may be stored in the disc storage
unit
or
on magnetic tape
and
recalled
as
necessary.
The third possible function is to
enter
data
via
the paper tape reader under program control.
This
is
not a normal usage, however, and is more of
an
exception than a rule to the intended
use of the reader.
Figur
e
12. Paper Tape Reader
Hardware Load
Hardware Load is
a
process whereby data is trans-
ferred from the paper tape reader to memory under
hardware control.
This is used for initial loadingof
programs, for the loading of maintenance diagnostics
when necessary, and for the
automatic
restart of
an
operating program upon discovery of a fault condition.
Hardware load may be
initiated
in five ways.
1.
Manually from the control console.
2.
By execution of a DIF 4 instruction.
3.
When
Q
counts down to -32.
4.
When the second LDQ instruction is executed
after
a
program interrupt occurs while in
the
operate
mode.
5.
When in the
operate
mode and
a
halt occurs.
w&u&~~u=
~@------------
I-22
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