Differences between Siemens PLCs


Thread Starter


Hi all

Can anybody answer the following questions:
1-What differences are between S5 PLC series and S7 PLC series?
2- What differences are between S7-200 and S7-300 and S7-400?

Best regards

Daniel Chartier

Hello, Farzad;
1) S5 and S7 are 2 distinct generations of Siemens PLCs. S5 satarted to come out in the late 1980s; they are programmed through a CPM/DOS-based software called Step 5. S7 PLCs started to come out in 1995, I believe. They are based on more recent and more powerfull microprocessor families; their software is Step 7, Windows-based and friendlier to use.

2) S7 PLCs are produced in Germany (S7-300 and 400) and in the USA (S7-200). The S7-300 and 400 are modular PLCs (basically all modules are seperate and have to be ordered seperately) and they use Step 7-Basis as a software. S7-200 PLCs were historically produced by engineers who came to Siemens with the purchase by Siemens of the PLC division of Texas Instruments; they developped a shoebox-type PLC (basically, a small processor with little memory and on-board IO) with a distinct software called Step 7-Microwin. Siemens has not been able to integrate the S7-200 into the S7-300 and 400 group. The software environment (instructions, memory maps, interfaces) is still distinct and incompatible.

Hope this helps,
Daniel Chartier
The S5 is the old stuff and the S7 is much more powerful, the programming is Windows based and is IEC compliant. Go with the S7.

As for the differences between the 200 and 300/400. The S7-200 is mainly a low end PLC (equivalent Horsepower of a SLC500) it is nicely featured and well priced. The S7-300/400 is the staple, an S7-300 is roughly equivalent to a PLC5. The 400 is the main processor for Process Controls or very large applications with up to 64mb of compiled code (you will run out of processor time first. The Siemens S7 (and S5) PLC are truely interupt driven so forget about scan time as you can make things happen as often as needed.

Heine Grünewald

Several things!!!!!!

- S7-200 (microcontroller) i a PLC for small applications and can only be programmed via special SW and small instructionset. low memory

- S7-300 is for the low-end and mid-end performance applications (Compact modules).

- S7-400 is for the mid-end and high-end performance (large modules).

Both s7-300 & S7-400 can be programmed via SIMATIC Manager.

Heine Grünewald