Differences between Siemens PLC S7-1200 and 200

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This post was last edited by zhoudingshengs on 2023-11-22 at 16:36. The Siemens S7-1200 is a compact controller, positioned between the existing SIMATIC S7-200 and S7-300 models. The differences between it and the S7-200 lie mainly in hardware, communication, engineering, memory, function blocks, counters, timers, and process functions. 1. Differences in hardware: In terms of hardware expansion, the S7-200 supports up to seven expansion modules, while the S7-1200 allows for up to eight signal modules and up to three communication modules. Taking the S7-200CPU224XP and S7-1200CPU1214C as examples, the CPU of the S7-1200 allows for an increase in the number of IO points via signal boards, whereas the number of IO points on the S7-200CPU is fixed. In terms of hardware configuration, the address auto-assignment for the S7-200 cannot be changed, whereas the addresses of the S7-1200 can be manually reallocated by the user. 2. Differences in communication: In terms of serial communication, both the S7-200 and S7-1200 support point-to-point communication via RS232 and RS485, and they accept communication protocols such as ASCII, USS, and MODBUS. The S7-200 requires an RS232 converter to enable RS232 serial communication, whereas the S7-1200 uses an RS232 communication module for such communication. The S7-1200 has a built-in PROFINET interface, enabling communication with programming devices, HMIs, and other CPUs. 3. In terms of engineering, the programming software STEP7 Basic for the S7-1200 provides an easy-to-use, integrated engineering framework that can be used for the configuration of SIMATIC S7-1200 systems as well as simplified HMI panels. 4. Differences in storage: The size of the program memory and data memory in the S7-200 is fixed, whereas those in the S7-1200 are variable. The symbol table and comments of the S7-1200 CPU can be stored in the CPU and are available online. In the S7-1200, symbolic access can be used to optimize the allocation of storage space for data blocks. In terms of maintaining storage areas, the S7-200 allows only the data area to be set for retention, whereas the S7-1200 can have up to 2048 bytes of retention space, enabling retention to be set for discrete variables within data blocks. In terms of storage card capacity, the S7-1200 can use storage cards with a maximum capacity of 24 megabytes; this is an optional feature for both the S7-200 and S7-1200, and the same types of data can be stored on them. Additionally, the memory card of the S7-1200 is also used to enable functions such as storage area expansion, program allocation, and firmware upgrading. 5. Different program structures: The S7-200 consists of a main program, subroutines, interrupt subroutines, and data areas such as area V, whereas the S7-1200 has OB blocks, SB blocks, FC blocks, and data blocks. The maximum nesting depth for calling subroutines in S7-200 is 8; all program blocks share a single common data block. In contrast, S7-1200, like S7-300, has FC, FB, and OB blocks, etc., offering a highly modular program structure that can be reused, with a maximum nesting depth of 16. In the S7-200, events are assigned to interrupts, and interrupt events trigger the corresponding subroutines. In the S7-1200, event allocation is done through organization blocks. 6. Different data types: The new data types in the S7-1200 make applications more flexible. For example, when used for time and date, the S7-200 needs to read the corresponding data in area V, whereas the S7-1200 can access all components of the DTL structure using symbolic names. 7. Differences in counter instructions: In the S7-200, the status bit of a counter is set when its count value is greater than or equal to the set value. For the counters of the S7-1200, the output is set when the count value is greater than or equal to the set value. The counting range of the S7-200 counter is from 0 to 32767, whereas that of the S7-1200 can be adjusted. 8. Differences in timer instructions: In the S7-200, the timer’s status bit is set when the timing value is greater than or equal to the set value. In the S7-1200, the timer outputs a set signal when the timing value is greater than or equal to the set value. Additionally, the timing time for the S7-1200 can be entered directly, without the need to use a timing base for conversion as is the case with the S7-200. 9. Differences in process functions: In terms of process functions, the S7-200 typically relies on wizards to carry out these tasks, whereas the S7-1200 uses corresponding blocks for that purpose.