Siemens S7-300PLC from entry to the master of 50 classic quiz(one)

1: How to avoid the "Communication Error" message when using the CPU 315F and ET 200S?

With the CPU S7 315F, ET 200S and fail-safe DI / DO modules, you call the fail-safe program of OB35. Also, you have accepted the 

default settings for all monitoring times and are willing to receive "Communication Failure" messages. OB 35 defaults to 100 milliseconds.

 You have set the F monitoring time of the F I / O module to 100 milliseconds so that the I / O module is addressed at least every 100 milliseconds.

 However, a communication fault occurs because OB 35 is called every 100 milliseconds. To ensure that there is a difference between the OB35 scanning

 interval and the F monitoring time, ensure that the F monitoring time is greater than the OB35 scanning interval.


S7 Distributed Security System up to V5.2 SP1 and 6ES7138-4FA00-0AB0, 6 ES7138-4FB00-0AB0, 6ES7138-4CF00-0AB0. 

In the new module, F monitoring time is set to 150 milliseconds.

2: What are the monitoring times for S7-300 CPUs on PROFIBUS when DP slaves are not available?

When operating a PROFIBUS network with DP slaves on the PROFIBUS interface of the CPU, you want to check during

 startup whether the desired and actual configurations match. Two different times are given on the Startup tab in the

 CPU Properties dialog box.

3: How to determine the power or buffer error, such as: battery failure?

The CPU operating system accesses OB81 if an event is triggered by a fault in the power supply (S7-400 only) or in

 the buffer. After error correction, revisit OB81. In the event of a battery failure, the S7-400 accesses OB81 only if the

 BATT.INDIC switch in battery test is active. If you have not configured OB81, the CPU does not enter the operating

 state STOP. If OB81 is not available, the CPU remains operational when the power supply fails.

4: What should you watch out for when assigning addresses to I / O modules (centralized or distributed) on the S7 CPU?

Please note that the data area created (eg a double word) can not be configured on the process image boundary 

because only the area below the boundary can be read into the process image in this data block, so it is not possible 

to access from the process image data. Therefore, these configuration rules do not support this situation: For example,

 configure an input double word on address 254 of a 256-byte process image. If you must be so sited, you must 

adjust the size of the process image accordingly (in the Properties of the CPU).

5: How to carry on the basic communication of global data in S7 CPU? What should I pay attention to when communicating?

Global data communication is used to exchange small capacity data. Global data (GD) can be: Inputs and outputs
Mark
Data in the data block
Timer and counter functions
Data exchange refers to the exchange of data in the form of data packets between CPUs connected to a one-way or

 two-way GD ring. The GD ring is identified by the GD ring number.
One-way connection: A CPU can send GD packets to multiple CPUs.
Bidirectional connection: Connection between two CPUs: Each CPU can send and receive one GD packet.
You must ensure that the receiving CPU does not acknowledge the reception of global data. If you want to exchange 

data via the corresponding communication block (SFB, FB or FC), you must make the connection between the 

communication blocks. By defining a connection, communication block design can be greatly simplified. This definition

 is valid for all calling blocks and does not need to be redefined every time.

6: Is it possible to use an S7-400 memory card for the CPU 318-2DP?

In normal operation, only "short"> memory cards with the order numbers 6ES7951-1K ... (Flash EPROM) and 

6ES7951-1A ... (RAM) can be used.

7: Why the CPU 31xC can not read the full input from the default addresses 124 and 125 despite the LED light?

For the following models of CPUs, check that 24V is connected to pin 1. The LED is controlled by the input current.

 The voltage of 24V on pin 1 needs further processing.


(6ES7 313-6BE0.-0AB0), 313C-2DP (6ES7 313-6CE0.-0AB0), 313C-2PTP 314C-2PTP (6ES7 314-6BF0.-0AB0)

8: What should I do if the PROFINET interface occasionally has a communication error when configuring the PN 

interface of the CPU 31x-2 PN / DP?

Make sure that all components (transitions) in Ethernet (PROFINET) support 100 Mbit / s full-duplex basic operation.

 Avoid center splitters splitting the network because these devices only work in half-duplex mode.

9: What is the meaning of the "clock" correction factor in the hardware configuration editor?

In the hardware configuration, via CPU> Properties> Diagnostics / Clock you can specify a correction factor in the 

"Clock"> field. This correction factor only affects the CPU's hardware clock. The time interrupt is derived from the 

system clock and has nothing to do with the hardware clock setting.

10: How to realize the bidirectional data transmission between master and slave through the 

function block in PROFIBUS DP?

The master plc can exchange data with the slave by calling SFC14 "DPRD_DAT" and SFC15 "DPWR_DAT", 

while for slaves it is possible to call FC1 "DP_SEND" and FC2 "DP_RECV" to complete the exchange of data.

11: What identification data can be read from the S7 CPU?

The following identification data can be read out with SFC 51 "RDSYSST":
You can read the order number and CPU version number. To do this, use SFC 51 with SSL ID 0111 and use the following

 index:
1 = module identification
6 = basic hardware identification
7 = basic firmware identification

12: How to program loadable communication function blocks FB14 ("GET") and FB15 ("PUT") for

 data exchange on S7-300 with CPU 317-2PN / DP?

In order to exchange data between two S7-300 stations using a CPU 317-2PN / DP over an S7 connection that is

 configured with NetPro, you must call the communication function blocks in S7 communication. Module FB14 ("GET")

 is used to retrieve data from the remote CPU and module FB15 ("PUT") is used to write data to the remote CPU.

The function blocks are included in the standard library of STEP 7 V5.3. <Properties of communication modules FB14

 ("GET") and FB15 ("PUT") of the CPU 317-2PN / DP:

FB14 and FB15 are asynchronous communication functions. The operation of these modules may span multiple OB1 

cycles. Activate FB14 or FB15 by entering the parameter REQ. DONE, NDR or ERROR indicates that the job is finished.

 PUT and GET can simultaneously communicate through the connection.


Note: You can not use the communication blocks in the library SIMATIC_NET_CP for the CPU317-2PN / DP.

13: What should you watch out for synchronizing the PtP jobs for the compact CPU 313C-2 PtP and CPU 314-2?

In user programs, you can not program SEND jobs and FETCH jobs at the same time.
which is:
The FETCH job (SFB 64) can not be called as long as the SEND job (SFB 63) is not completely terminated (DONE or ERROR)

(Even when REQ = 0).


SEND jobs (SFB 63) can not be called as long as the FETCH job (SFB 64) is not completely terminated (DONE or ERROR)
(Even when REQ = 0).


When dealing with an active job (SEND job, SFB 63 or FETCH job, SFB 64), a passive job can be processed at the same 

time
(SERVE Job, SFB 65).

14: Can MICR. Is the master 420 to 440 operating as a configuration axis (position external detection) with the CPU 317T?

Yes, but in terms of power and accuracy, the requirements for the configuration axis vary widely. The servo drive 

SIMODRIVE 611U, MASTERDRIVES MC or SINAMICS S must be operated with the CPU 317T under high demands. 

The MICROMASTER series also meets the power and accuracy requirements at low demands.

15: How do you configure direct data exchange (inter-node communication) between two CPU modules configured as DP slaves?

The two CPU stations are configured as DP slaves and are operated by the same DP master, the communication 

between them being done by DX for the direct exchange of data by configuring the exchange mode.

16: How to communicate with SFC65, SFC66, SFC67 and SFC68?

For unidirectional basic communication, data is read from a passive station using the system function SFC67 (X_GET) 

and data is written to a passive station (server) using the system function SFC68 (X_PUT). These blocks are only called 

in the active station. For a bidirectional basic communication, the system function SFC65 (X_SEND) in the called station,

 in which you want to send data to another active station. In the also active active receiving station, the data is recorded 

via the system function SFC66 (X_RCV).


In both types of basic communication, user data of up to 76 bytes can be processed per block call. Data consistency is 8

 bytes for S7-300 CPUs and full-length for S7-400 CPUs. If connected to the S7-200, you must consider that the 

S7-200 can only be used as a passive station.

17: What is the free allocation of I / O address?

The free assignment of addresses means that you can freely assign an address to each module (SM / FM / CP).

 The assignment of addresses is done in STEP 7. First define the start address, the module's other address to it 

as a benchmark.


Advantages of freely assigning addresses: Because there is no address gap between modules, the available address 

space can be optimally used. When creating standard software, the configuration of the S7-300 involved can be 

disregarded in the assignment of addresses.

18: diagnostic buffer can do?

Identify sources of failure faster, thereby increasing system availability. Evaluate the last event before STOP and look

 for the cause of the STOP.


The diagnostic buffer is a circular buffer with a single diagnostic entry that appears in the sequence of occurrences; the

first entry shows the most recent event. If the buffer is full, the oldest event will be overwritten by a new entry.

 Depending on the CPU, the size of the diagnostic buffer is either fixed or can be set via parameters in HW Config.

19: What are the entries in the diagnostic buffer?

1) Fault events
2) Operation mode transitions and other operational events that are important to the user
3) User-defined diagnostic event (with SFC52 WR_USMSG)
In the operating mode STOP there is as few memory events as possible in the diagnostic buffer so that the user can easily

 find the cause of the STOP in the buffer. Therefore, the entry is stored in the diagnostic buffer only if the event 

requires the user to generate a response (such as scheduling a system memory reset, the battery needs to be charged), 

or important information must be registered (such as a firmware update, a station fault).




20: How to determine the size of MMC in order to complete the STEP 7 project?
In order to select the right MMC for your project, you need to know the size of the entire project and the size of the block 

to

 load. The size of the project can be determined as follows:


1) First archive the STEP 7 project. Then open the archived item in Windows Explorer and determine its size (check the 

item 

and right-click). This will tell you the size of the archive.


2) Load the block into the CPU. Now still need to select "PLC> Module Information> Memory". Here, in "Load memory 

RAM + EPROM", 

you can see the size of the allocated load memory.


3) This value must be added to the size of the archived item that has been determined. This gives you the total amount 

of memory required to save the entire project on one MMC.

21: CPU reset after a full set of what will be retained?

When resetting the CPU, the memory is not completely erased. The entire main memory is completely erased, but

 loading data in memory, as well as data stored on a Flash-EPROM memory card (MC) or Micro Memory Card (MMC), 

is fully preserved. In addition to loading the memory, the timers (except for the CPU 312 IFM) and the diagnostic 

buffer are also retained. The CPU with MPI interface or a combined MPI / DP interface retains the current address and 

baud rate used by the interface until all resets occur. On the other hand, another PROFIBUS address is also completely 

deleted and can no longer be accessed.


Important: After resetting the PG / PC, communication with the CPU can only be established via the MPI or MPI / DP 

interface.