65
04/99 AWB 2700-1311 GB
6 Operation
Power-up behaviour
The PS 4-300 runs a system test when the power is
switched on. The PLC then switches to the “Ready”
or “Run” state if no hardware errors are detected.
The system test consists of the following routines:
Memory test
Hardware test
Operating system test
User program test
The results of the test are indicated by the “Ready”,
“Run” and “Not Ready” LEDs. If the test is
successful, these LEDs are lit continuously; if an error
is detected, they flash.
The “Run” and “Not Ready” LEDs will flash if the PLC
does not have an operating system, and the PLC is
in boot status.
The PLC’s status depends on the position of the
operating mode selector switch (See Table 10).
Shutdown behaviour
The PLC’s power supply detects when the power
supply is switched off. Voltage dips of
≤
10 ms can be
bridged by the power supply unit. If a longer voltage
dip occurs, the internal 5 V supply remains stable for
at least another 5 ms. The microcontroller uses this
time to save all the data needed to restart in the
memory areas provided for this purpose.
H1311g.bk Seite 65 Freitag, 4. Juni 1999 1:12 13
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