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Editor's Notes

• #4: Monitoring Functions Diagnosis is important in the operating phase of a system or machine. Diagnosis usually occurs when a problem (disturbance) leads to standstill or to the incorrect functioning of the system or machine. Due to the costs associated with downtimes or faulty functions, the associated cause of the disturbance has to be found quickly and then eliminated.
• #6: Module Information The Module Information function reads the most important data from the directly connected module. You will find additional information in the individual tabs: General: Among other things, the module description, hardware and firmware versions Diagnostic Buffer: It contains all diagnostic events in the order they occurred. All events are listed in plain text and in the order they occurred in the display. Memory: Size and usage of the EPROM load memory, RAM load memory and the work memory. Scan Cycle Time: Displays the monitoring time selected, the shortest, the longest and the current cycle time Time System: Displays the real-time clock and the integrated run-time meter Performance Data: Displays the integrated system blocks and the available organization blocks as well as address areas (I,Q,M,T,C,L) Communication: Displays the performance data of the communication interfaces and the connection overview Stacks: Information on the contents of the I Stack, B Stack and L Stack. For this, the CPU must be in the STOP state or have reached a breakpoint.
• #7: Diagnostic Buffer The diagnostic buffer is is a FIFO buffer in the CPU‘s battery-backed memory area. The diagnostic buffer contains all diagnostic events in the order in which they occurred. The diagnostic buffer cannot be deleted by a memory reset. All events can be displayed on the programming device in plain text and in the sequence in which they occur.
• #9: Opening a Block For so-called synchronous errors, that is, for errors that were triggered by a faulty instruction in the user program, you can open the interrupted block by clicking on the "Open Block" button. If the STL language is selected, the cursor is positioned directly in front of the instruction that caused the interruption. In LAD/FBD, the network causing the interruption is displayed.
• #11: The contents of all relevant registers at the time of the interruption are displayed in the I Stack screen: •AccumulatorsYou can select the numbers format for displaying the accumulator contents in the "Display Format" list. •Address RegisterYou can select the numbers format for displaying the address register contents in the "Display Format" list. •Status WordBits 0 to 7 of the status word are displayed. They are identified with abbreviations according to their meaning.
• #13: Diagnosing Hardware The function opens the station that can be accessed online and gives you information about the status or operating mode of the modules. You can see that there is diagnostic information for a module when you see the diagnostic symbols that indicate the status of the associated module or the operating mode of the CPU. When you double-click the symbol, a screen with further information pops up. In the example shown, the analog input module (slot 7) has triggered a diagnostic interrupt. As a result, the CPU has gone into the STOP mode. Both modules have been given symbols accordingly. By double-clicking the CPU, you would see the diagnostic buffer. By double-clicking the analog module, you would be given the relevant diagnostic data. In the example, the external auxiliary voltage (supply voltage) of the analog module has failed.
• #14: Monitor/Modify Variables The Variable Address Table (VAT) is used to view (monitor) and change (modify) a CPU memory area‘s address value in a defined format. The "Monitor/Modify Variables" function is started from the SIMATIC Manager or from the LAD/STL/FBD Editor. • Address: absolute address of the variable. • Symbol: symbolic name of the variable • Symbol comment: comment on the variable displayed • Display format: a data format you can choose per mouse click (such as binary or decimal), in which the contents of the variable is displayed • Status value: value of the variable in the selected status format • Modify value: value to be assigned to the variable To check the input and output wiring (regardless of the user program), you can also call the Monitor/Modify Variables tool (VAT) directly from the HWConfig tool
• #15: Trigger Point You can establish the trigger points for Monitoring and Modifying using Variable -> Set Trigger... or by using the icon shown here on the left. The "Trigger Point for Monitoring" specifies when the values of the variables being monitored on the screen are to be updated. The "Trigger Point for Modifying" specifies when the given modify values are to be assigned to the variables being modified.
• #16: Function With Force, you can overwrite variables with any values you like, independent of the user program. You can open only one Force Values window for a CPU. With the S7-300™, you can only force the process image inputs and outputs; with the S7-400™ you can also force bit memories and peripherals. Notes • You can only cancel a force job by selecting the Variable -> Stop Forcing menu option • You cannot undo "Forcing" with the Edit -> Undo menu option. • You cannot cancel the force job by closing the Force Values window or by exiting the "Monitor/Modify Variables" application.
• #20: Area of Use The Cross References (list) gives you information about how which addresses are used in which blocks. Thus, you can find out, for example, where in the entire user program a memory bit is (double) assigned. You open the cross references with View -> Cross References or by clicking the icon you see here on the left.
• #24: Filtering Cross References You can also use the Filter function to display individual addresses or address areas separately. You access the Filter reference data dialog through the View menu. The entries in the Filter Dialog have the following meaning: •…with NumberThe filter area specifies the address area to be displayed. You can also specify several partial areas. The filter area entry "10-50; 70; 100-130" means that the address 70 and the address area from 10 to 50 and from 100 to 130 is to be displayed.