IBM Series 1 User Manual page 166

INTEGRATED DIGITAL I/O ELECTRICAL CHARACTERISTICS
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Each digital input (or process interrupt) point is
nonisolated
and is designed to operate with TTL compatible
voltage levels. Voltaye inputs up to
±24
volts may
be used
with this feature. Figure 5-4 shows a representative input
point. Note that for voltage above +5 volts,
the input
impedance is a function of the input voltage. Each DI point
has
an
internal pull-up
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and unconnected inputs are
held at the inactive state (up level).
Each DI point and the external sync input meets the
following specifications:
Input impedance:
Input limits:
Logic one:
Logic zero:
~9.2 kilohms at less than +4.5V
~2
kilohms at +24V
+24 Vdc maximum
-24 Vdc minimum
~1.0 volts
~2.5 volts
Respon.2~ !im~.
59 microseconds. Response time is the time
between the points at which the user1s input meets and
maintains the required voltage for the logic one level and
the
50'
point of the resulting interrupt request in the
PI
mode. This
time includes an envelope of 5 microseconds in
which the card could be performing a Read
PI
or Read
PI
With
Reset command.
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The D1 inputs must be stable for a
minimum of 1 microsecond prior to and after the activation
of external sync. Changes during this time result in
unpredictable data in the D1 register.
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Characteristic§
Each digital output point is a non isolated, solid-state
current sink point as represented by the equivalent circuit
in Figure
5-5.
When operated without a user-source voltage,
each point generates TTL compatible
voltage levels. When
operated with a user source higher than +5 volts, each point
operates as an open collector, solid-state current sink.
Each point
is capable of sinking 100 mA in the "on" state.
There is no restriction on the number of DO points sinking
maximum current simultaneously.
Integrated Digital I/O 5-9