S7-300 Common Issues (1)

11: What identification data can be read from the S7 CPU? The following identification data can be read via SFC 51 “RDSYSST”: the order number and CPU version number can be read. To this end, use SFC 51 and SSL ID 0111 along with the following indices: 1 = Module identifier, 6 = Basic hardware identifier, 7 = Basic firmware identifier. 12: On an S7-300 equipped with a CPU 317-2PN/DP, how can communication function blocks FB14 (“GET”) and FB15 (“PUT”) be programmed for data exchange? To enable data exchange between two S7-300 workstations using CPU 317-2PN/DP through an S7 connection configured with NetPro, communication function blocks must be called in S7 communication. Module FB14 (“GET”) is used to retrieve data from a remote CPU, while module FB15 (“PUT”) is used to write data to a remote CPU. The function blocks are included in the standard library of STEP 7 V5.3. Attributes of the communication modules FB14 (“GET”) and FB15 (“PUT”) of CPU 317-2PN/DP: FB14 and FB15 provide asynchronous communication functions. The operation of these modules may span multiple OB1 loops. Activate FB14 or FB15 by entering the parameter REQ. DONE, NDR, or ERROR indicates that the job has ended. PUT and GET can communicate over the connection simultaneously. Note: The communication blocks in the SIMATIC_NET_CP library cannot be used with CPU317-2PN/DP. 13: What considerations are needed for the simultaneous processing of jobs on the compact CPUs 313C-2 PtP and CPU 314-2 PtP? In the user program, it is not possible to program both SEND and FETCH jobs simultaneously. In other words, as long as the SEND job (SFB 63) has not been completely terminated (with a status of DONE or ERROR), the FETCH job (SFB 64) cannot be called (even when REQ=0). As long as the FETCH job (SFB 64) has not been completely terminated (DONE or ERROR), the SEND job (SFB 63) cannot be called (even when REQ=0). When processing an active job (SEND job, SFB 63 or FETCH job, SFB 64), an inactive job (SERVE job, SFB 65) can also be processed simultaneously. 14: Can the MICROMASTER 420 to 440 be used as configuration axes (for external position detection) and operated together with the CPU 317T? Yes, but in terms of power and precision, the requirements for the configured axes vary greatly. Under demanding conditions, the servo drives SIMODRIVE 611U, MASTERDRIVES MC, or SINAMICS S must be used in conjunction with the CPU 317T. Even under low-demand conditions, the MICROMASTER series can meet the requirements for power and precision. 15: How to configure direct data exchange (inter-node communication) between two CPU modules that have been set up as DP slaves? The two CPU stations are configured as DP slaves and are operated by the same DP master; direct data exchange between them can be achieved by setting the communication mode to DX. 16: How to use SFC65, SFC66, SFC67, and SFC68 for communication? For one-way basic communication, the system function SFC67 (X_GET) is used to read data from a passive station, while the system function SFC68 (X_PUT) is used to write data to a passive station (server). These blocks are only called in the active station. For a two-way basic communication, the system function SFC65 (X_SEND) in the calling station is used, where data is to be sent to another active station. In the similarly active active receiving station, the data will be recorded through the system function SFC66 (X_RCV). In the basic communication of these two types, each block call can handle up to 76 bytes of user data. For the S7-300 CPU, the data consistency for data transfer is 8 bytes, while for the S7-400 CPU it is the full length. If connected to an S7-200, it must be taken into account that the S7-200 can only be used as a passive station. 17: What is free allocation of I/O addresses? Free address allocation means that you can freely assign an address to each type of module (SM/FM/CP). Address allocation is carried out in STEP 7. First, define the starting address; the other addresses of this module are based on it. Advantages of free address allocation: Since there are no address gaps between modules, the available address space can be utilized optimally. When creating standard software, the configuration of the involved S7-300 can be ignored during address allocation. 18: What can a diagnostic buffer do? Identify the source of faults more quickly, thereby improving system availability. Evaluate the last event before the STOP and identify the cause of it. The diagnostic buffer is a circular buffer with a single diagnostic entry, which are displayed in the sequence of events that occur ； The first entry shows the most recent events. If the buffer is full, the earliest occurring event will be overwritten by the 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) Changes in operation mode and other operation events that are important to the user 3) User-defined diagnostic events (using SFC52 WR_USMSG). In STOP operation mode, as few events as possible should be stored in the diagnostic buffer, so that the user can easily identify the cause of the STOP state in the buffer. Therefore, entries are stored in the diagnostic buffer only when an event requires the user to take action (such as scheduling a system memory reset, charging the battery) or when important information must be recorded (such as firmware updates, station failures). 20: How to determine the size of MMC to store a STEP 7 project completely? To select the appropriate MMC for a project, it is necessary to understand the size of the entire project as well as the size of the blocks to be loaded. The size of a project can be determined using the method described below: 1) First, archive the STEP 7 project. Then open the archived item in the Windows Resource Explorer and determine its size (select the item and right-click). This will tell you the size of the archived file. 2) Load the block into the CPU. It is still necessary to select "PLC > Module Information > Memory". Here, in “Load memory RAM + EPROM”, the size of the allocated load memory can be seen. 3) This value must be added to the size of the archived items that have already been determined. This allows one to determine the total amount of memory required to store the entire project on an MMC.

21: Which settings are retained after a complete CPU reset? When the CPU is reset, the memory is not completely erased. The entire main memory is completely erased, but the data loaded into memory, as well as the data stored on Flash-EPROM memory cards (MC) or micromemory cards (MMC), remains intact. In addition to loading into memory, timers (except for CPU 312 IFM) and diagnostic buffers are also retained. A CPU with an MPI interface or a combined MPI/DP interface retains the current address and baud rate used by the interface only until a full reset occurs. On the other hand, another PROFIBUS address was also completely deleted and can no longer be accessed. Important note: After resetting PG/PC, communication with the CPU can only be established through the MPI or MPI/DP interface. 22: Why can’t CPU be accessed online via MPI? If the MPI parameters have already been changed on the CPU, please check the hardware configuration. These values can be compared with the parameters under “Set PG/PC interface” to check for any inconsistencies. Alternatively, you can do this: open a new project and create a new hardware configuration. Set the respective values for address and transfer speed in the properties of the CPU’s MPI interface. Write the “empty” item to the memory card. Insert the memory card into the CPU and then reapply voltage to it, so that the settings stored on the memory card can be transferred to the CPU. The current settings of the MPI interface have now been transmitted, and in this way, a connection can be established as long as the interface is not faulty. This method is applicable to all S7-CPUs with a memory card interface. 23: What is the purpose of the error OB? If the described error occurs (see Document 1), the corresponding OB will be called and processed. If the OB is not loaded, the CPU enters STOP mode (exceptions: OB70, 72, 73, and 81). The S7-CPU can identify two types of errors: 1) Synchronization errors: These errors occur during the execution of specific operations and can be attributed to certain parts of the user program. 2) Asynchronous errors: These errors cannot be directly attributed to the running program. These errors include priority-related errors, errors in automated systems (faulty modules), or redundancy-related errors. 24: Which “fault OBs” should be programmed in the DP slave or the 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 for diagnostic interrupts, OB 86 for sub-rack faults, and OB 122 for I/O access errors. 1) Diagnostic OB82: If a module that supports diagnostics and for which a diagnostic interrupt has been enabled detects an error, it sends a request for a diagnostic interrupt to the CPU both for incoming events and for outgoing events. The operating system then calls OB82. OB82’s own local variables contain the logical base address of the defective module and 4 bytes of diagnostic data. If you have not programmed the OB82 yet, the CPU enters the “stop” mode. You can block or delay the diagnosis interruption of OB, and release it again through SFC 39 - 42. 2) Sub-rack fault OB86: If a DP master system or a distributed I/O station is detected to be faulty (for both incoming and outgoing events), the operating system of that CPU invokes OB 86. If there is no programming OB 86 but such an error occurs, the CPU enters the “stop” mode. You can block or delay OB86 and release it again through SFC 39 - 42. 3) I/O access error OB122: When an error occurs while accessing the data of a module, the operating system of that CPU calls OB 122. For example, if the CPU detects a read error while accessing the data of a single module, the operating system then calls OB 122. This OB 122 operates with the same priority class as the interrupt block. If programming OB 122 is not performed, the CPU changes from the “running” mode to the “stopped” mode. 25: Why are reserved areas rewritten in some cases? In STEP 7’s hardware configuration, several operand areas can be defined as “reserved areas”. This allows the content in these areas to be retained even after a power loss, even in the absence of a backup battery. If a block is defined as a “reserved block” and it does not exist in the CPU or has only been temporarily installed, then part of the content in those areas will be overwritten. After the power is turned on/off, other information can be found in the relevant sections. 26: Why can’t the contents of a flash memory card be loaded into an S7 300 CPU? Your project is on the flash card. Now use it to load the S7 300. But after the loading was complete, it was found that the RAM in the CPU was still empty. The reason for this problem is that there are \"incorrect\" organizational blocks in your program that cannot be processed (for example, OB86 lacks a DP interface). After resetting and restarting the CPU, the RAM remains empty. The diagnostic buffer will provide some information regarding this \"unable to load\" block. 27: The diagnostic address when using the CPU315-2DP as a slave and as a master. When configuring a CPU315-2DP station, you use the S7 tool “H/W CONFIG” to assign the diagnostic address. If a fault occurs, these diagnostic addresses are added to the variable “OB82_MDL_ADDR” in the diagnostic OB. You can analyze this variable in OB82 to identify the faulty station and take appropriate action. Here is an example of how to assign a diagnostic address: Step 1: Configure the slave device using the CPU315-2DP and assign it a diagnostic address, such as 422. Step 2: Configure the master station using the CPU315-2DP. Step 3: Connect the configured slave stations to the master station and assign them a diagnostic address, such as 1022. 28: What settings are required on the DP slave interface of an S7-300 CPU in order to use it for routing? If a CPU is used as the I-Slave and also acts as an S7 router, please note the following: The DP interface of the slave used for routing selection must be set to active. This can be done in HW Config: in the properties dialog for the DP interface, the options “Commissioning/Test operation” or “Programming, status/modify...” must be activated. The precautions regarding these settings can be found in the table below. For S7 routing connections, there are 4 available connection resources – independent of any other connection resources. No connection resources using PG/OP or S7 basic communication. If it is necessary to establish a connection with a communication partner located on its rack through the DP interface (as in CP 343-1), a routing connection must also be used. For connections to a communication partner located on the same rack via the MPI interface, routing connection resources are not used, as it is possible to reach the partner directly in this case. Note: This does not apply to CPU 318. 29: Why is there no return value when using the internal timing table of the S7-300 CPU? When parameterizing the system function blocks SFC2, SFC3, and SFC4 for CPUs 312IFM to 316-2DP, if an identifier greater than “B#16#0” is specified for a runtime schedule, an error will occur and the desired functions will not be available. In this case, the identifier “8080h” will be output at the “RETVAL” output of the block. Note: For these CPUs, only one timer is available. Therefore, you should use only the identifier “B#16#0”. Within a cycle block (OB1, OB35), the system function SFC2 \"SET_RTM\" must not be called; instead, it should be invoked during the restart of OB (OB100). You can also initiate this block using an external trigger. Otherwise, the block will keep resetting the running timer and will never be able to complete the counting. 30: How are variables stored in temporary local data? The L stack always starts at address “0”. In the L stack, the same number of bytes is reserved for each data block to store the static or local data associated with that block. When a block is terminated, its space is also released accordingly. The pointer always points to the first byte of the currently open block. 31: Is the runtime counter also reset after the CPU has been fully reset? When using the S7-300, there is a difference between CPUs with a hardware clock (an internal \"real-time clock\") and those with a software clock. For CPUs with software clocks that lack a backup battery, the value of the runtime counter is erased after the CPU is completely reset. For CPUs with hardware clocks that have a backup battery, the final value of the runtime counter is retained after the CPU is completely reset. Similarly, the runtime counter of CPU 318 and all S7-400 CPUs retains its last value after the CPU is completely reset. 32: How can I configure S7 CPUs that are not part of the same project as DP slaves for my S7 DP master module? By default, in STEP 7, only one S7 CPU can be configured as a slave, provided that it is within the same project. The station then appears as “CPU 31x-2 DP” in the hardware directory under “PROFIBUS-DP > Configured Stations”. Using this approach, a connection between the DP master station and the DP slave station can be established. There is also an option to configure an S7 CPU that is not in the same project as the master station as a slave station. Proceed as follows: Configure the DP slave in the conventional manner. Download the GSD file for the S7-300 CPU to be used as a slave station from the Internet. This file is located under “PROFIBUS GSD Files / SIMATIC” on the customer support website. Open SIMATIC Manager and hardware configuration. Open “Options > Install new GSD...”, and insert the newly downloaded GSD file into the hardware directory. (Note: No windows need to be opened in HW Config during this process.) Update the hardware directory by going to “Options > Update Directory”. You can now configure your DP master station. The S7-300 CPU as a slave can be found under “PROFIBUS-DP > More Field Devices > SPS”. Note: If the DP slave is connected manually, make sure that the bus parameters, the PROFIBUS address of the DP slave, and its I/O configuration are identical in both projects. 33: Is the impact of a power outage without a backup battery the same as a complete reset? It’s different. When the CPU is completely reset, its hardware configuration information is deleted (except for the MPI address), the programs are removed, and the remaining magnetic memory is also cleared. If the power is turned off without a spare battery and memory card, the hardware configuration information (except for the MPI address) and the program are deleted. However, remanent magnet memory is unaffected. If the program is reloaded under these conditions, it will use the old values stored in the residual magnetism memory while operating. For example, these values usually come from the first 8 counters. Failing to take this into account can lead to dangerous system conditions. Recommendation: Without a spare battery and memory card, always perform a full reset after powering off. 34: To connect a 2-wire sensor to the analog input of a compact CPU? 2-wire and 4-wire sensors can be connected to the analog input terminals of the CPU 300C. When using a 2-wire sensor, set “I = Current” as the measurement type in the hardware configuration, just as with 4-wire sensors. Note: Please be aware that compact CPUs only support active sensors (4-wire sensors). If passive sensors (2-wire sensors) are used, an external power supply is required. Warning: Please be aware of 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 (breakdown limit). For such situations (for example, applying current limiting to a 2-wire sensor or connecting a PTC thermistor in series with the sensor), ensure that sufficient protection is provided. 35: Can SM322-1HH01 also operate at a load voltage of 24 V AC? Yes, you can also use the SM322-1HH01 with a load voltage of 24 V AC. 36: What is the minimum load voltage and current required to ensure that the SM322-1HF01 is powered on? The SM322-1HF01 relay module requires 17 V and 8 mA to ensure proper operation. For the lifespan of the contacts, such a value is better than the value given in the manual for this module (10 V and 5 mA). The specified values in the manual should be considered as the minimum requirements. 37: Which 24V digital input modules (6ES7 321-xBxxx- ...) need to be powered? The table below shows the power plug connections (L+ / M) for the 24V digital input module. 38: Can the SM321 module (DI16 x 24V) also be used in the ET200M? The module SM321 (MLFB 6ES7 321-7BH00-0AB0) can also be used in the ET200M. Among them, the CPU 31x-2DP serves as the DP master station, or the communication processor CP CP342-5 acts as the DP master station. Similarly, this module can be connected to an S7-400 CPU via an ET200M and the S7-400 communication processor CP443-5. 39: What is the address occupied by the SM323 digital card? The SM323 module is available in a 16-bit version (6ES7 323-1BL00-0AA0) and an 8-bit version (6ES7 323-1BH00-0AA0). For 16-bit type modules, the input and output occupy the addresses “X” and “X+1”. If the base address of SM323 is 4 (i.e., X=4 ； If the slot is 5), then the inputs are addressed at addresses 4 and 5, and the output addresses are also addressed at addresses 4 and 5. In the module’s wiring view, the input byte “X” is located at the top on the left, while the output byte “X” is at the top on the right. For 8-bit type modules, the input and output each occupy one byte, and they share the same byte address. If fixed slot addressing is used, with the SM323 inserted into slot 4, the input addresses are I 4.0 to I 4.7, and the output addresses are Q 4.0 to Q 4.7.

41: What must be taken into consideration when performing direct I/O access? 　　 It should be noted that in an S7-300 configuration, if direct I/O read access across modules is performed (reading several bytes at once using this command), incorrect values will be obtained. The specific address can be viewed in hardware. 　　 42: Does the SM321 module need to be connected to DC 24V? 　　 It isn’t necessary; if the MLFB is an SM 321 module of type 6ES7 321-1BH02-0AA0, then there is no need to connect a DC 24V supply. See figure: 43: How to plan the simulation module SM374 in STEP 7 hardware configuration, and how to find this module in the hardware catalog? 　　 The simulation module SM374 can be used in three modes: as a 16-channel digital input module, as a 16-channel digital output module, and as a mixed digital input/output module with 8 inputs and 8 outputs. 　　Now configure SM374 according to the module you need to simulate, that is to say ； 　　 If SM 374 is used as a 16-channel input module, then a 16-channel input module should be configured – the recommended model is SM 321: 6ES7321-1BH01-0AA0. If SM 374 is used as a 16-channel output module, then a 16-channel output module should be configured – the recommended model is SM 322: 6ES7322-1BH01-0AA0. If SM 374 is used as a mixed input/output module, then a mixed input/output module (8 inputs, 8 outputs) should be configured – the recommended model is SM 323: 6ES7323-1BH01-0AA0. 　　 　　44: When measuring current, a short circuit occurs in the sensor – will the analog input I+ of module 6ES7 331-1KF0.-0AB0 be damaged? 　　 When measuring current and a sensor short circuit occurs, the analog input I+ of module 6ES7 331-1KF0.-0AB0 is not damaged. This module has built-in overcurrent protection. > Each 50-ohm resistor in the module is preceded by a PTC element to prevent damage to the module’s input channels. 　　 Please note that the permitted long-term maximum input voltage is 12V, and the temporary (up to 1 second) value is 30V. 　　 　　45: If the CPU is disconnected, will the 2-wire measurement transmitter continue to be powered? 　　 If the transmitter module is inserted in position “D” and is powered by an external voltage at pins 1 and 20, the 2-wire transducer continues to be powered. Even if the CPU is disconnected, its power supply current remains unchanged. 　　 　　46: When using the S7-300 analog input module to measure temperature in Fahrenheit, can the absolute error limits listed in the module’s documentation be used? 　　 The specified error limit cannot be used directly. Both the basic error and the operational error are expressed in absolute temperature and Celsius temperature. It must be multiplied by the coefficient 1.8 to convert it to Fahrenheit units. 　　Example: S7-300 AI 8 x RTD: The specified operating error for the temperature input is +/−1.0 degrees Celsius. When measured in Fahrenheit, the acceptable maximum error is +/−1.8 degrees Fahrenheit. 　　 　　47: Why can’t a commercial digital multimeter be used to measure the constant current used for reading impedance at the analog input terminal? 　　 Almost all S5/S7 analog input devices still operate in a complex manner, that is, all channels are connected sequentially to a single AD converter. This principle also applies to the constant current required for reading impedance. Therefore, the current flowing through the resistor for reading is only used for short-term readings. For the SM331-7KF02-0AB0, which has one selected interface for suppressing \"50Hz\" and 8 parameterized channels, this means that current will flow approximately every 180 ms, with 20 ms available each time to read the impedance. 　　 　　48: Why is the voltage output of the analog output module of the S7-300 outside the tolerance range? What are the purposes of terminals S+ and S-? 　　 The following description applies to all analog output modules SM 332: When using the analog output module SM 332, attention must be paid to the assignment of the return inputs S+ and S-. They serve to compensate for the characteristic impedance. When the two contacts of the actuator are connected with separate wires labeled S+ and S-, the analog output adjusts the output voltage so that the actual voltage at the actuating mechanism becomes the desired voltage. 　　 To obtain compensation, the actuator must be connected with 4 wires. This means that for the first channel, it is required that: the output voltage be connected to the actuator via pin 3 and pin 6. 　　 Assign pins 4 and pin 5 to the actuator. 　　 If you do not want to receive compensation, simply cross-connect pins 3-4 and pins 5-6 at the switch ahead. 　　 Note: Due to the open sensor terminals (S+ and S-), the output voltage is adjusted to a maximum of 140 mV (for 10V). g For this allocation, it is not possible to maintain a voltage output tolerance limit of 0.5 %. 　　 　　49: How to connect a potentiometer to 6ES7 331-1KF0-0AB0? The sampling terminal and the leading terminal of the potentiometer are connected to M+, the trailing terminal is connected to M-, and S- is connected to M-. 　　Note: The maximum resistance that can be used is 6K. If the potentiometer supports direct output of a variable voltage, then its terminal should be connected to V+, and its middle terminal to M-. 　　

50: How to connect a PT100 temperature sensor to the analog input module SM331? 　　 The resistance value of a PT100 thermistor changes as the temperature changes. If a constant current flows through the thermistor, the voltage drop across it varies with temperature. A constant current is applied to the contacts Ic+ and Ic-. The simulation module SM331 measures the changes in current at the M+ and M- electrodes. The temperature can be determined by measuring the voltage. 　　There are three types of connections from the PT100 to the analog input module: a 4-wire connection provides the most accurate measurement values. 　　 　　 　　***Note: 1) The formula for 3-wire connection only illustrates the actual measurement process for the analog input module SM331 (with MLFB code 6ES7 331-7Kxxx-0AB0) b ". 　　 2) In the S7-300 series, there are some analog input terminals that allow for multiple measurements. They specify the wire resistance of the common return line and perform mathematical compensation. The achieved accuracy is almost comparable to that of a 4-wire connection. An example of such a module is the SM331 (MLFB number 6ES7 331-7PF00-0AB0). 　　 3) The given formula is still applicable to the main physical relationships, but it does not include an effective measurement procedure for determining the PT100 resistance. 　　 　　51: Can a HART measurement converter be connected to the standard analog input modules of the SIMATIC S7-300 series? 　　 If other HART features of the HART measurement converter are not required, other S7-300 analog input modules can also be used. For example, the module 6ES7 331-7KF0x-0AB0 can be used, or a 4-channel module with isolation such as 6ES7 331-7RD00-0AB0. To this end, the integration time should be set to 16.66 ms, 20 ms, or 100 ms. For connection to or communication with a handheld device, a 250-Ohm resistor must be connected in series in the circuit. 　　 Note: If you want to program a HART measurement converter via a controller (for example, SIMATIC PDM), a corresponding HART module must be used (such as 6ES7 331-7TB00-0AB0 or 6ES7 332-5TB00-0AB0). 52: How to avoid fluctuations in the analog input of the SM335 module? 　　 The following wiring instructions apply to the analog input/output modules of the following MLFB models: 6ES7335-7HG00-0AB0, 6ES7335-7HG01-0AB0. Check whether an ungrounded sensor mounted on an insulated frame is being used, or verify whether your sensor is grounded. 　　 Sensors mounted on insulated frames: Connect the ground terminal Mana (pin 6) to the measurement channels M0 (pin 10), M1 (pin 12), M2 (pin 14), and M3 (pin 16), as well as to the central ground point (CGP), via the shortest possible path (directly to the front-end connector if possible). 　　 Grounding sensor: Ensure the sensor has a proper equipotential connection. Then isolate the connections from M to Mana and to the central ground point. Please place the shielding layer on both sides. 　　 　　53: In the S7-300F, can the error checksum and standard modules be used together in the central rack? 　　 On the central frame of the S7-300F, error-proof and non-error-proof (standard) digital I/O modules can be used together. To this end, just as in the ET200M, an isolation module (MLFB: 6ES7195-7KF00-0XA0) is required to isolate the error-proofing modules from the standard modules in the central and expansion racks. 　　Please follow the following installation principles: Standard modules (IM, SM, FM, CP) must be inserted into the slots on the left side of the isolation module, while error-proof digital E/A modules must be inserted into the slots on the right side of the isolation module. 　　 　　54: Can sensors/actuators from Zone 0 or Zone 1 be connected directly to the S7-300 Ex(i) module? 　　 Sensors/actuators from Explosion Protection Zone 0 cannot be connected. But sensors/actuators from Explosion Zone 1 can be connected directly. 　　 The Ex(i) module is tested according to IIC. Therefore, the module has two explosion-proof barriers. However, approval must be obtained in order to use sensors/actuators in Zone 0. (The module should have three explosion-proof barriers.) 　　 　　55: What special considerations should be taken when using FM 355 or FM 355-2 in SIMATIC PCS 7? 　　 For example, if you want to use FM 355 or FM 355-2 in a redundant ET 200M station, please note the following important points: There are two function blocks available for connecting the FM 355. For example, if you need the \"replace modules during operation\" (hot-swapping) function, you can utilize the advanced features of the IM 153-2 HF interface module with order number 6ES7 153-2BA00-0XB0. In this case, when using the “Hardware Configuration” software for setup, you must activate the “Replace modules during operation” (hot-swapping) function. IM 153-2 and all SM/FM/CPs must be connected to the activated bus module (order number 6ES7 195-7Hxxx-0XA0). 　　 　　56: What are the precautions when connecting the output of the first FM 352-5 directly to the input of the second FM 352-5? 　　 To interconnect two FM352-5s, this can be achieved using the 6ES7 352-5AH10-0AE0 (P-type sunk output). 　　 The 6ES7 352-5AH00-0AE0 features an M-type sinking output, which is available only when a plug-in resistor is connected to each output terminal; the recommended specifications for such resistors are 2.2 kOhm / 0.5 W. Ensure that there is a short-circuit connection inside the switch box. In such cases, the operating frequency can reach up to 100 kHz. 　　 　　57: Can the FM353/FM354 be replaced without using PG? 　　 Sure. FM353 (MLFB No. 6ES7 353-1AH01-0AE0) and FM354 (MLFB No. 6ES7 354-1AH01-0AE0) can be replaced without a PG. 　　 Requirements: Use the configuration package FM353 V2.1 or FM354 V2.1, along with STEP 7 version V3.1 or later. 　　 Step: After completing the startup of FM and the system, it is necessary to create a system data block (SDB >= 1000) and store it on the PG. All the parameterized data of FM is stored in this SDB (DB/travel programs, machine data, incremental size tables, etc.). Transfer this SDB to the CPU or to the storage card of the CPU. 　　 　　57: How to directly read the count values and measurement values by accessing the I/O on FM 350-2? 　　 FM 350-2 allows up to four count values or measurement values to be displayed directly on the module I/O. The “Specify Channel” function can be used to define which individual measurement value is to be displayed in the I/O area. Depending on the size of the counted or measured value, the data format must be parameterized as “Word” or “Dword” in the “User Type”. If parameterized as “Dword”, each “user type” can have only one count value or measurement value. If parameterized as “Word”, two values can be read in. In user programs, the command L PIW is used for Word access, and L PID is used for Dword access. 　　 　　58: How should a Siemens 6FX2001-5 (Up=24V; SSI) absolute encoder be connected? 　　 See figure: 59: What should be noted when using an absolute encoder with FM357‑2? When the firmware version of FM357‑2 is V3.2/V3.3, the sampling values from the absolute encoder may be incorrect; these issues will be resolved once the firmware version is upgraded to V3.4. 　　 1) FM357－2 failed to start. For example, lose power within the time defined in the startup window. 　　 2) Remove and reinsert the encoder cable of FM357-2 while it is in operation. 　　 3) The simulated scenario shows that Long@??FM357-2 is ready to run without any drive. 　　 　　60: How to quickly download an initial value into the counter series FM350-1 or FM450-1? 　　 For some applications, it is important to reset the counter to its initial value as soon as a certain comparison value is reached. Furthermore, a series of calculations are usually required during reset to determine the next comparison value (in order to optimize the intersection of the materials). Even without the standard function FC CNT_CTRL, it is possible to choose to perform a reset. 　　 To reset the counter quickly, configure the counter as follows: in the \"Basic Parameters\" section of the \"Properties\" dialog box for the counter module, set the option \"Generate interrupt\" to \"Yes\", and then set the interrupt selection to \"Process\". In this way, an interrupt is generated during reset. Configure digital output DQ0 in the “Output” parameter settings to activate it when the comparison value is reached. In the “Set Counter” field of the “Input” parameter flags, set the option to “Multiple”. 　　 Note: In the associated channel data block, the bit DBX 27.0 or DBX 27.1 (CTRL_DQ0) must be set to 1 so that the settings are applied in the correct direction. In the “Interrupt Release” parameter options, select “Set Counter” so that the interrupt is triggered when a rising edge occurs at the digital input SET. The digital input I2 of the function modules FM 350-1 / FM 450-1 is used to reset the counter to its initial value. This input is connected to the digital output Q0 (same as FM 350-1 / FM 450-1). 　　 Note: In the data block of the associated channel, the data word DBD 14 (LOAD_VAL) must be preset to an initial value (such as L#0) in advance. The data word DBD18 (CMP_V1) must be set to the comparison value. These values must be transmitted to the FM using FC CNT_CTRL by setting the corresponding trigger bit on the FC once

　　80: What should be done when STEP 7 cannot be uninstalled? 　　 Try to uninstall STEP 7 through the control panel. If the installation file is damaged, uninstalling the program often results in errors, along with error messages. Additionally, the STEP 7 CD contains the file Simatic STEP7.msi. STEP 7 can be uninstalled using this file. 121: How to determine if there is a power supply issue, such as a battery problem? If an error in the power supply (only S7‑400) or the buffer triggers an event, the CPU operating system accesses OB81. After correcting the error, access OB81 again. In the event of a battery fault, if the BATT.INDIC switch in battery detection is activated, the S7-400 accesses only OB81. If OB81 is not configured, the CPU will not enter the STOP operating state. If OB81 is unavailable, the CPU remains operational in the event of a power supply error. 122: How to diagnose an analog template? The CPU can interrupt the execution of user programs to process diagnostic alarm block OB 82. In the user program, you can call SFC 51 or SFC 59 in OB 82 to obtain more detailed diagnostic information from the template. The diagnostic information remains consistent until OB 82 exits; when OB 82 exits, a diagnostic interrupt response will be generated for the template. 123: For flip-flops with low-power inputs, how can circuit damage be avoided? Connect the trigger to the SM322-8BF; if the power input of its 1 signal is below 10 mA (for example, 1 mA), it may report a line fault. It is not recommended to disable the “Wire breakage” diagnosis, as this will disable all diagnoses, and the SM322-8BF may not be able to be switched on and off safely when operating within a certain current range (0.5 to 10 mA). Remedy: Connect a resistor in parallel with the trigger, so that there is at least 10mA of current (24V at approximately 2.4 kOhm). This resistor should be placed directly on the trigger, so that circuit damage can be easily detected. 124: How to update the operating system for an S7 318-2 CPU? Requirements for creating an operating system update card: 1. Type of S7 memory card: 2 MB flash memory, part numbers 6ES7 953-8LM00-0AA0, 6ES7 951-1KL00-0AA0. 2. STEP 7 V3.1 or a newer version. 3. A PC or programming device (PG) with an external PROM programmer to program the memory card. Steps to create an operating system update card using STEP7: 1. Download the required CPU files ； 2. Double-click the file name to unzip the file ； 3. In Simatic Manager, execute “File/S7 Memory Card/Delete” to delete the contents of the micro memory card ； 4. In Simatic Manager, select “PLC/Update CPU Operating System” to program the operating system. Select the target directory and “open” the CPU_HD.UPD file to start the programming process ； 5. When the standard mouse pointer reappears, programming of the operating system update card is complete. Performing operating system updates: 1. Turn off the power (PS) to the rack where the CPU is located ； 2. Insert the prepared operating system update card into the CPU ； 3. Turn on the power supply (PS) of the rack where the CPU is located ； 4. The operating system is transferred from the micro memory card to the internal CPU flash EPROM. At this point, all of the CPU’s LEDs will light up (INTF, EXTFFRCE, <span lang="EN-GB">CRST, RUN, <span lang="EN-GB">STOP). 5. The operating system update is completed after about 2 minutes; at this time, the STOP LED will flash slowly => requesting a reset of the system memory ； 6. Turn off the power and insert the micro memory card required for the operation ； 7. When the power is turned on, the CPU performs an automatic memory reset, after which it immediately enters the ready state. . Note: To perform the update, the battery must be removed from the module. 125: How is the signal conversion time for analog templates calculated? The conversion time consists of the basic conversion time plus the following additional processing times for the template: 1) resistance testing, 2) open circuit monitoring. The basic conversion time depends directly on the conversion method used for the template – whether it is integral calculation or instantaneous value conversion. For the integral calculation method, the integration time has a direct impact on the conversion time; this integration time is determined by the interference frequency suppression settings in STEP 7. 126: Is it possible to run a DP network between two DP slaves? No. It is not possible to establish slave-to-slave communication. A master station is always required to operate the DP network. Intelligent slaves can access the initial values of other slaves (through direct data communication), but a DP master is always required to control the DP network. Smart slaves can also operate independently without using a DP network (standalone operation), but they cannot serve as DP masters. It can only work in conjunction with the module interface. 127: For some analog input templates, you can use STEP 7 to set the smoothing exponent for the analog values – what is the purpose of this? Use of smoothing exponent: The smoothing exponent for the simulated values ensures a stable simulated signal for further processing ； This is very important for adapting to the slow changes between the simulated value and the measured value, such as in temperature measurement. Smoothing principle: The measured value can be smoothed through digital filtering, which is achieved by using a template to calculate an average value based on a specified number of converted digital and analog values ； Users can assign smoothing parameters across up to four levels: low, average, high; these four levels determine the number of analog signals used for the averaging calculation ； The higher the selected smoothing level, the more stable the smoothed analog value will be, and the longer it will remain stable before the smoothed analog signal becomes applicable after a step response. 128: Should analog signal cables be grounded at one end or at both ends? To reduce electronic interference affecting analog signals, twisted-pair shielded cables should be used; the shielding layer of such cables must be grounded at both ends. However, if there is a potential difference between the two ends of the cable, it will generate equalizing current in the shielding layer, causing interference with the analog signal; in such a case, you should ground one end of the cable’s shielding layer. 129: The analog signal value is 7FFFH. What is the reason? Each analog input template can provide a measured value of 7FFFH, which is independent of the parameter values at the time a fault is detected; this measured value can correspond to an overflow fault or to a situation where the channel is not enabled. 130: What are the common measures taken to prevent the risk of electrostatic discharge? Ensure proper grounding: When handling equipment that is sensitive to static electricity, it is necessary to ensure that the working surfaces and packaging are properly grounded in order to prevent the accumulation of static charge. Avoid direct contact: Touch static-sensitive equipment only when it is unavoidable; for example, when performing repairs, hold the template but do not touch the pins of the components or the conductors on the printed circuit board. This method prevents the discharge energy from affecting the static-sensitive equipment. If measurements must be taken using a template, it is necessary to first touch a grounded metal part to discharge electricity from the body. This method is only applicable to grounded measuring equipment.