Siemens SIMATIC S7-1200 Інструкція з програмування безпеки - Сторінка 32

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3 Methods for Safety Programming

Create a data type for the data from the HMI to the safety program. Use this data

type in the HMI tags, in the data buffer for the safety program and in the standard

user program where the data is copied.

To add more tags to be written from the HMI to the safety program, merely modify

this data type.

Figure 3-13: Copying data from the HMI to the safety program in the standard user program

Safe signal transmission

Communication between the HMI and the CPU is not safe. Transferring safety-

related data requires measures that ensure the safe transfer.

This application example shows a suitable safety concept:

https://support.industry.siemens.com/cs/ww/en/view/67634251

Resetting safety functions

For resetting safety functions or acknowledging errors using an HMI, TIA Portal

provides the "ACK_OP" system block.

An acknowledgment consists of two steps:

1. Change in/out IN to value "6" for exactly one cycle.

2. Change in/out IN to value at input "ACK_ID" for exactly one cycle within one

minute.

This system block is an exception to the recommended data exchange.

In each cycle, the system block resets the "IN" InOut parameter to "0". If the data

from the HMI is copied in the standard user program, "0" is overwritten with the

value from the HMI in each cycle and the condition that the values are present for

exactly one cycle is not met.

Therefore, write the tag at the "IN" input directly from the HMI and set the safety

program priority higher than that of communication to avoid potential data

corruption.

Figure 3-14: "ACK_OP" system block

Safety Programming Guideline

Entry ID: 109750255,

V1.0,

10/2017