Description:
The non-fail-safe output V_MOD of the F channel drivers F_CH_AI and F_PA_AI and the values RAW_VALUE and V_MOD from the AL_STATE structure of the F_CH_AI do not behave as described in the programming and operating manual "Configuring and Programming S7 F/FH Systems, Edition 07/2007" and in the associated Online Help. To achieve the behavior described for V_MOD and AL_STATE , you must add another block between the output V_MOD of the F channel driver and the evaluating blocks. These changes are not part of the safety program.

Note:
This FAQ cannot be applied in block types.

Procedure
First, you must dearchive the "Support_zip" library attached to this FAQ.

Using F_CH_AI
There are 2 blocks available in the attached library for using F_CH_AI. CH_V_MOD (FC) simply provides the updated output V_MOD. CH_V_AL (FB) provides the updated output V_MOD and AL_STATE.

• Copy the relevant blocks from the attached library into the block container of your S7 program. Change the FC/FB numbers if necessary.
• Place a CH_V_MOD or CH_V_AL next to each F_CH_AI whose V_MOD or AL_STATE output you are evaluating.
• Connect the output V_MOD of the F_CH_AI to the input IN of the block concerned.
• Use the V_MOD or AL_STATE outputs required of this block for the evaluation.

The following figure shows how CH_V_MOD is used in the CFC.

Fig. 01

The following figure shows how CH_V_AL is used in the CFC.

Fig. 02

• Place the instance of CH_V_MOD or CH_V_AL in the runtime sequence each time directly in front of the first evaluating block (in front of MEAS_MON in the present example).

Using F_PA_AI

• Copy the PA_V_MOD block from the attached library into the block container of your S7 program. Change the FC number if necessary.
• Place a PA_V_MOD next to each F_PA_AI whose V_MOD output you are evaluating.
• Connect the output V_MOD of the F_PA_AI to the input IN of the PA_V_MOD.
• Only use the V_MOD output of the PA_V_MOD for the evaluation.

Fig. 03

• Place the instance of the PA_V_MOD in the runtime sequence each time directly in front of the first evaluating block (in front of the MEAS_MON in the present example).

Support_.zip ( 29 KB )

Keywords:
Safety Integrated, F Systems