The main class is one of the programmable logic controller and module difference was S7-200 belonging to the basic entry level, while S7-300 and S7-400 relative to the use of higher-end. Siemens plc is the serial number of the product.
---->S7 200: in the electric control system for small, focused on logical control;
---->S7 300: for larger systems, can realize the complexity of process control, such as PID, PWM, etc;
---->S7 400: used for large scale control system, mainly redundancy control.
200 belongs to small machine, 300 belongs to medium machine, minicomputer is multifunctional machine, will all function combined in with, it of control scale for maximum 512 points, CPU of operation processing speed than in the mainframe fast, minicomputer more for overall type of, extended module up can added 8 block, applies Yu small equipment, price high; in the mainframe structure is module of of, up can added more than 300 more block extended module, in the mainframe hardware more your, cost high, but its operation processing speed fast, has is strong of communications function, Mainly used in large-scale production line, such as the chemical industry, paper industry, steel industry, car production line, air conditioning, sewage treatment, and mainframes in the Siemens 300 and 400 in China, Siemens stable performance, network communication is powerful, simple, and cost-effective.
And hardware differences:
(1) major S7-300/400 more modular, S7-200 series is integral, CPU module, the I/O module and the power supply module in a module, called CPU modules and S7-300/400 series, from the power supply, I/O,CPU is a separate module. But that misleading 200 series cannot be extended, in fact, 200 series can also be extended, bought the CPU module is integrated with the merely functional, some smaller systems do not require additional custom modules, 200 series modules also have signaling, communication, control and other modules.
(2) to rack 200 series no concept, called Guide; in order to facilitate control, 300/400 series module was mounted on a rail, called a rack, is an extended frame corresponding to the Central rack, rack also is reflected in the software.
(3) on the same rack 200 series module by module directly above the data connectors contacts; and 300/400 are at the bottom of the u-bus connector.
(4) 300/400 series I/O input is connected to the front connector on the, on the module front connector attached to the signal, and is not directly connected to I/O signals on the signal module so that you can replace signaling modules without rewiring.
(5) 300/400 series CPU with PROFIBUS (PROFIBUS is an international. The open. Not dependent on the device manufacturer's field-bus standard) interfaces.
Second, software differences:
(1) STEP7-Micro/WIN32 for 200 series software 300/400 use STEP7 software, with the Micro and without the difference is quite obvious.
(2) there are three programming languages--of the 200 series statement list (STL), ladder diagram (LAD), function block diagram (FBD); 300/400 series in addition to the three, but also has structured control language (SCL) and graphic language (S7 graph).
(3) 300/400 software features provide a number of blocks of data to each functional block (Block-FB), called Instance.
(4) 300/400 can't feel free to customize the Organization Block and the sub-routine and Interrupt routine, now the OB1 self-centered, nothing the system will call it, the rest of what became FB-Block and FC-, others are predefined system, System s to them (SFB and the SFC) defined his identity.
(5) 300/400 are provided in the accumulator (ACCU) and status word register, Diagnostics buffer.