Bit 6 Reserved.
Bit 7 This bit
is
initially reset
by
the hardware
power-on
cycle. Then it is set and reset
by
the IBM Personal
Computer.
Setting this bit inhibits the sending
of
interrupts to the IBM Personal Computer,
but
it does
not
prevent setting the interrupt/status bit
(0-5).
If
an interrupt
is
set when the Mask bit is on, subsequent
removal
of
the Mask bit will allow
that
interrupt to
pass through to the IBM Personal Computer.
Scan Code Register (2DS)
This
8-bit
register
is
internal to the emulation adapter and
is
set
and reset by the IBM Personal Computer. This register requires
one address.
In
3278/79
Emulation mode, this register
is
used by the IBM
Personal Computer to send a keystroke code to the control unit.
The IBM Personal Computer will
not
change the contents
of
this
register if bit 3
of
the Control Register is set.
Note: The scan code placed in this register must be the
ones-complement
of
the data to be sent to the control unit.
1-9
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