Siemens S7-300PLC from entry to the master of 50 classic quiz(two)
22: Why can not access the CPU online via MPI?
If you have changed the MPI parameters on the CPU, check the hardware configuration. You can compare these values
with the parameters under "Set PG / PC interface" to see if any inconsistencies exist.
Or you can do this: Open a new project and create a new hardware configuration. Set the respective values for the
ddress and transfer speed in the properties of the MPI interface of the CPU. Write the "empty" item to the memory card.
Insert the memory card into the CPU and turn on the voltage of the CPU again to transfer the settings on the memory
card to the CPU. The current settings of the MPI interface have now been transmitted and, as such, the connection can
be established as long as there is no fault on the interface. This method is suitable for all S7-CPUs with a memory card
interface.
23: What is the purpose of the error OB?
If one of the errors described (see file 1) occurs, the corresponding OB is called and processed. If this OB is not loaded,
the CPU goes to STOP (exceptions: OB70, 72, 73 and 81)
The S7-CPU recognizes two types of errors:
1) Synchronization error: These errors are triggered during the processing of a specific operation and can be attributed to
a specific part of the user program.
2) Asynchronous Error: These errors can not be directly attributed to the running program. These errors include priority
class errors, errors in the automation system (faulty modules), or redundant errors.
24: Which "fault OBs" should be programmed in the DP slave or CPU315-2DP master?
When configuring a CPU315-2DP station as a slave, the following OBs must be programmed in the STEP7 program in order
to evaluate error messages of the distributed I / O type:
OB 82 Diagnostic interrupt OB, OB 86 Subrack fault OB, OB 122 I / O access error1) Diagnostic OB82: If a module that supports diagnostics and has released a diagnostic interrupt for it recognizes an error,
it issues a request for a diagnostic interrupt to both the incoming event and the outgoing event. The operating system
then calls OB82. The OB82 own local variable contains the logical base address of the defective module and 4 bytes of
diagnostic data. If you have not programmed OB82, the CPU enters "stop" mode. You can interrupt or defer diagnostics
interrupt OBs and release them again via SFC 39 - 42.
2) Sub-rack fault OB86: OB 86 is called by the operating system of the CPU if it is detected that a DP master system or a
distributed I / O station is faulty (both for incoming events and outgoing events). If you did not program OB 86 but an
error occurred, the CPU goes into STOP mode. You can block or delay OB86 and re-release it via SFC 39 - 42.
3) I / O access error OB122: An error occurred while accessing the data of a module, the operating system of the CPU
calls OB 122. For example, when a CPU recognizes a read error while accessing data from a single module, the operating
system calls OB 122. The OB 122 operates in the same priority class as the interrupt block. If you have not programmed
OB 122, then the CPU is changed from Run mode to Stop mode.
25: Why in some cases reserved area will be rewritten?
In the STEP 7 hardware configuration, several operand areas can be defined as "reserved areas". This allows you to
maintain the contents of these areas even after you have powered down even without a backup battery. If you define a
block as a "reserved block," and it does not exist in the CPU or is only temporarily installed, portions of those areas are
overwritten. After the power is turned on / off, other contents will be found in the relevant area.
26: Why can not I load the contents of the flash memory into the S7 300 CPU?
Your project is on a flash card. Now use it to load the S7 300. But after loading found CPU RAM is still empty. This problem
occurs because of unhandled, "wrong" organization blocks in your program (for example, OB86 does not have a DP
interface). After resetting and restarting the CPU, the RAM is still empty. Diagnostic buffer for this "can not be loaded"
block will be prompted for some information.
27: When using CPU315-2DP as slave and CPU315-2DP as master when diagnosing address
When configuring a CPU 315-2DP station, you assign the diagnostics address using the S7 tool "H / W CONFIG". If a fault
occurs, these diagnostic addresses are added to the variable "OB82_MDL_ADDR" of the diagnostic OB. You can analyze
this variable in OB82, identify the faulty station and react accordingly.
Here's an example of how to assign a diagnostic address:
Step 1: Configure the slave via CPU 315-2DP and assign a diagnostic address, eg 422.
Step 2: Configure the master via the CPU315-2DP
Step 3: Link the configured slave to the master and assign a diagnostic address, such as 1022.
28: What settings need to be made for the DP slave interface of an S7-300 CPU before it can be used for routing?
If you are using a CPU as an I-Slave and the CPU also functions as an S7 router, take note of the following:The DP interface of the slave for routing must be set active. This can be done in HW Config: The option "Commissioning /
Test operation" or "Programming, status / modify ..." must be activated in the properties dialog of the DP interface.
Considerations for these settings can be found in the following table.
For S7 routed connections, there are 4 available connection resources - independent of any other connection resource.
Connection resources without PG / OP or S7 basic communication are not used.
If you have to establish a connection via the DP interface to a communication partner located in its rack (as in the CP 343-
1), a routing connection is also used. As for the connection to a communication partner located on its rack via the MPI
interface, however, no routing connection resources are used, since in this case, the partner can be reached directly.
Note: This does not apply to CPU 318.
29: Why do I have no return value when using the internal runtime of the S7-300 CPU?
When you specify an identifier greater than "B # 16 # 0" for a run-time schedule for the CPU 312IFM to 316-2DP
parameterizing the system function blocks SFC2, SFC3 and SFC4, then an error and the required function are not possible
use. In this case, the identifier "8080h" is output at the "RETVAL" output of the block.
Explanation: Only one timer is available for these CPUs. So you should only use the identifier "B # 16 # 0". The system
function SFC2 "SET_RTM" must not be called in a cycle block (OB1, OB35), but it should be called at the restart OB
(OB100). You can also start the block with an external trigger. Otherwise, the block will always reset the running
chronograph, can never complete the count.
30: How is the variable stored in the temporary local data?
The L stack always starts with the address "0". In the L stack, the same number of bytes are reserved for each data block
as static or local data held by each block.
When a block ends, then its space is also released again. The pointer always points to the first byte of the currently open
block.
31: Is the run time counter reset after the CPU has been fully reset?
When using an S7-300, there is a difference between a hardware clock with a built-in "real-time clock" and a CPU with a
software clock. For CPUs that have no software battery backed-up battery, the run-time counter has its last value erased
after the CPU has been fully reset. For those CPUs with a backup battery's hardware clock, the last value of the run-time
counter is retained after the CPU has been fully reset. Likewise, the run-time counters for CPU 318 and all S7-400 CPUs
retain their last value after the CPU is completely reset.
32: How to configure an S7 CPU not in the same project as a DP slave for my S7 DP master module?
By default, only one S7 CPU can be configured as a slave in STEP 7 if the station is in the same project. This station then
appears as "CPU 31x-2 DP" in the hardware catalog under "PROFIBUS-DP> Station that has already been configured".
In this way, you can set up a link between the DP master and the DP slave.
There is also an option to configure an S7 CPU that is not in the same project as the master as a slave. Proceed as
follows:
Configure the DP slave as usual.
Download the GSD file of the S7-300 CPU to be used as slave from the Internet. This file is located under "PROFIBUS GSD
File / SIMATIC" on the customer support web site.
Open the SIMATIC Manager and the hardware configuration.
Open the "Options; install new GSD ..." and insert the GSD file just downloaded into the hardware catalog. (Note: There
is no need to open any windows in HW Config during this process)
Update the hardware catalog with "Options; Update Catalog". <
You can now configure your DP master. The S7-300 CPU as a slave can be found under "PROFIBUS-DP> More Field
Devices> SPS".
Note: If this is done manually with the DP slave, to ensure bus parameters, the PROFIBUS address of the DP slave and
its I / O configuration must be identical in both projects.
33: The impact of power outage without reserve battery is the same as with full reset?
Different. When the CPU is completely reset, the hardware configuration information is deleted (except for the MPI
address), the program is deleted, and the remanent memory is also cleared.
Power off without backup battery and memory card, hardware configuration information (except MPI address) and
program are deleted. However, the residual magnetic memory is unaffected. If you reload the program in this situation,
it uses the old value of remanent memory while it is working. For example, these values usually come from the first eight
counters. If you do not take this into account, can lead to dangerous system state.
Recommendation: Always have a look at a complete reset after a power outage without a spare battery and memory card.
34: Is it possible to connect a 2-wire transducer to the analogue input of a compact CPU?
2-wire and 4-wire transducers can be connected to the analog input of the CPU 300C. When using a 2-wire transducer,
the "I = current" is set in the hardware configuration as the measuring type, in the same way as the 4-wire transducer.
Note: Please note that the compact CPU only supports active sensors (4-wire transducer). If you use passive sensors
(2-sensor), you must use an external power supply.
Warning: Please note the maximum allowable input current. 2-wire sensors may exceed the maximum allowable current in
the event of a short circuit. The maximum allowable current specified in the technical data is 50mA (sabotage limit). For
this situation (for example, applying a current limit to a 2-wire transducer or a PTC thermistor in series with the transducer),
ensure adequate protection is provided.
35: Can the SM322-1HH01 work at a load voltage of 24 VAC?
Yes, you can also use the SM322-1HH01 with a load voltage of 24 VAC.36: To ensure that SM322-1HF01 turn on the minimum required load voltage and current?
The SM322-1HF01 relay module requires 17 V and 8 mA to ensure proper switching. For contact life, this value is better
than the value of this module (10 V and 5 mA) provided in the manual. The manual's stated value should be considered
as the minimum required value.
37: What 24V digital input modules (6ES7 321-xBxxx- ...) need to be connected to the power supply?
24V Digital Input Module Power Pin Connection (L + / M).38: Can I use the SM321 module (DI16 x 24V) in the ET200M?
The module SM321 (MLFB 6ES7 321-7BH00-0AB0) can also be used in the ET200M. Which CPU 31x-2DP as a DP master
or communication processor CP342-5 as a DP master. The module can also be connected to an S7-400 CPU via the
ET200M and the S7-400 communication processor CP443-5.
39: What is the address occupied by SM323 digital card?
The SM323 module has two types of 16-bit type (6ES7 323-1BL00-0AA0) and 8-bit type (6ES7 323-1BH00-0AA0). For
16-bit type modules, the inputs and outputs occupy two addresses, "X" and "X + 1". If the base address of the SM323
is 4 (ie, X = 4; slot is 5) then the input is addressed at addresses 4 and 5 and the output address is also addressed at
addresses 4 and 5. In the wiring view of the module, the input byte "X" is at the top left and the output byte "X" is at the
top right.
For 8-bit types, each input and output occupies one byte and has the same byte address. If fixed slot addressing, SM323
is inserted into slot 4, the input address is I 4.0 to I 4.7 and the output address is Q 4.0 to Q 4.7.
