Siemens S5-135U/155U appendix Configuring

Analog Input/Output Modules

Configuring You must observe the following when configuring systems:

Switching on

Switching off

At the latest 100 ms after power-up of the PLC, the voltage must be present at the enable inputs of the I/O modules.

When the PLC has been switched off, the voltage at the enable inputs of the I/O modules must still be present as long as the internal 5 V voltage is present.

However, you must ensure that the 24 V load supply for analog output modules is switched off together with the PLC. If the supply voltage is still present at the modules and the PLC is switched off, the output values can drift.

(The analog holding elements for the outputs will no lon- ger be refreshed with the current value, because there is no 5 V supply to the modules from the bus.)

Switching Off the

CC

Separate or Common Shutdown of the CC/EU and Load Power Supply

You should observe the following instructions for switching off CCs and equipment for supplying power to the enable inputs.

When there is a need to switch off the load power supply separately without affecting the enabling of modules, there are the following possibilities for producing the enable voltage. These exist even when the load power supply is used without an additional capacitor and common shutdown.

S230 V AC supply for CC/EU and load power supply

a)	b)	Battery
±951	I/O Modules	c)
	F+
CC/EU	L+
Power Supply	L+
230 V AC
Load Power Supply 24V

Supply for the enable inputs from:

a)6ES5 951-4LB11 load power supply

b)Battery

c)Terminals for 24 V on the front plate of the power supply

9-100	System Manual
	C79000-G8576-C199-06