2.
All inputs are read including input registers.
3.
If the controller has been started, the RUN light on the controller is
illuminated and the unit starts solving logic at network 1.
When power is applied to the mainframe, the power supply begins
producing DC power. There is a slight delay between the time the DC
voltages are within regulation and the processor begins operating. This
delay allows sufficient power to be stored to ensure that proper power-
down procedures can be performed by the processor when external power
is removed.
Upon an indication of power failure, appropriate information is stored to
permit an orderly start-up, the RUN light is extinguished, and all outputs
turned OFF.
4.1.2 Power-Down Sequence
When power is removed, the controller continues to operate using the
power stored during the power-up sequence. If power is not restored within
l/lOth of a second, the controller executes an orderly power-down
sequence. The controller can operate for a longer time depending upon the
devices (Programmer, l/O modules, etc.) that are connected to the
mainframe at the time of power-down. Prior to actual loss of DC power, a
warning signal is provided from the power supply to the processor. This
warning signal causes the processor to stop solving logic wherever it is in
the scanning process, and to begin the power-down sequence.
The power-down sequence is performed to completion even if power is
restored. The power-down sequence requires less than 1110th of a second.
During the power-down sequence, the controller calculates and stores a
value for the contents of the random access memory. This value is used
during power up to verify the content of memory. In addition, all outputs are
turned OFF. The status of coils and the contents of registers are retained
for use during the power-up.
If it is necessary to remove power from the unit, remove power from the
controller first. Removing power from the I/O first, or at the same time as
the controller, can cause incorrect data to be stored during the power-down
sequence (if the controller was running at the time power was removed).
4.2 P370 PROGRAMMER OPERATION
Plugging the P370 Programmer into the mainframe supplies power to the
programming panel and enables the processor to initiate a diagnostic test
of the Programmer circuits. The COMM-OK status display should
illuminate. During this sequence, scan time is increased significantly.
All liquid crystal display segments turn on allowing the user to visually
verify that all the segments are operating (turned on). Refer to Figure 4-1
for an illustration of the P370 displays.
4-2
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