Safety Integrated - Industry - Siemens

Sample Code
Preliminary Remarks
Enclosed, we offer you the STEP 7 project as sample code in
which readback is demonstrated.
The sample code is always assigned to the components used
in the functional examples and implements the required functionality.
Problems not dealt with in this document are to be
implemented by the user; the sample code may serve as a basis.
Password
In all cases, the passwords used for the safety-relevant part is
„siemens“.
Use of the STEP 7 Project
A three-phase asynchronous motor is started via a push button
(NO) and stopped via a push button (NC). In case of emergency
the motor can also be stopped via an emergency stop
push button.
This functionality is used as a framework to show how the signals
are read back from the actuator and evaluated within the
STEP 7 program.
Download
The download is available via the following link:
http://support.automation.siemens.com/WW/view/en/
21331098
To call the corresponding project file open the
"f07_readback_v10.zip" file offered as separate download (on
the HTML page) and extract it into a user-defined directory.
To download the project to the F CPU please proceed as follows:
■ First load the hardware configuration into the S7-CPU
■ Switch to the SIMATIC Manager
■ Select the "Blocks" folder
■ Menu "Options" -> Edit safety program
■ Click the "Download" button
The sample code with the given configurations enables the
following:
■ Starting and stopping a three-phase asynchronous motor
considering the signals read back from the actuator.
■ Emergency stop for shutdown in case of a fault.
Note
The focus of this functional example is to demonstrate
how the readback signal is connected to the hardware
and how it is evaluated using software (STEP 7). Running
the motor is a means to an end. The emergency
stop functionality is used for safety reasons if the example
is reproduced.
Program procedure
The standard user program basically consists of two networks
in OB1:
Network 1
"K1_HELP"
"K2_HELP"
The auxiliary contacts of K1 and K2 are evaluated under the
memory bit FEEDBACK in the safety program.
Network 2
"START"
"STOP"
"INSTANZ_
FB1".EN
The switch-on condition COND="1" is only possible if the R input
of the flip-flop is on "0" signal (if "1" signal at S and R input
the reset function is predominant in this flip-flop).
INSTANZ_FB1.EN characterizes the signal state of a flip-flop in
the safety program (used as static variable in the safety program).
As long as a necessary acknowledgement has not been
transmitted in the safety program this bit remains on "0" and
it cannot be started.
The information of the flag "COND" is read as flag COND1 in
the safety program. This assignment takes place in the cyclic
interrupt OB 35 for the following reason:
Note
The reason below also applies to the memory bit
FEEDBACK from network 1.
&
"FL_P" "SR"
P
SR
S
>=1
R Q
"FEEDBACK"
=
"COND"
=
Functional Example No. AS-FE-I-007-V10-EN 255
G_FB_XX_147
G_FB_XX_148
Ex. No.
7