IBM Series 1 User Manual page 235

The power supplies for the processor and I/O expansion units
provide
five
regulated DC output voltages: +5.0, +8.5,
+12.0, -5.0, and -12.0 volts. Both supplies contain
overvoltage, undervoltage, and overcurrent protection.
Should overvoltage or undervoltage occur, the condition
initiates
d
power supply shutdown sequence.
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The
power-on
reset
siqnal is
provided to assure the state of the logic during power on
and off. The signal is TTL compatible. Logical one (up)
lev~l is between +2.6V and 5.5V. Logical 0 (down) level is
between O.OV and +O.4V. The power-on reset signal starts at
the TTL down level. When the +5V, -SV, and +8.5V are within
operational limits, this signal
goes to the TTL up level
after
a 500
millisecond delay. Should any ot the
three
voltages go approximately J% below their minimum tolerances,
this signal goes to the
TTL
down level.
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If
a
user incorporates a
technology such
that voltage
sequencing
must
occur
within a
given period of time (>350ms), the following method can
possibly be used. Assume that, for substrate biasing
purposes, Vn=-5.0V and Vh=8.5V; if Vn
1S
more positive than
-3.SV, Vh must not remain above +S.OV for more than 500ms.
Although no true sequencing occurs, after approximately
350ms the power supply circuitry checks to see that the
voltages are at an operational level, if not, the supply
shuts down:
oth~~rwise
the sequencing is met and the
technology is protected.
2-74
GA34-00J3