55
04/99 AWB 27-1184 GB
6 Operation
Power-up behaviour After the power supply is switched on, the PS4-200
carries out its own system test. The PLC then
switches to the “Ready” or “Run” status if no
hardware errors have been found.
The system test consists of the following routines:
Memory 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 light up briefly when the
power supply is switched on; if not, they blink.
The PLC's status depends on how the operating
mode selector switch is set (see Table 13).
Shut-down behaviour The power supply unit of the PLC 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 a further 5 ms. This time is used by
the microcontroller to save all the data required for a
restart in the memory ranges provided for this
purpose.
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