I am new user of Siemens s7-200 (Cpu212)PLCs. I want to write tachometer program in Siemens,up to some point I have achieved to do so. But at high speeds I can not read the signal from motor shaft. One of my friend said to me that I should use high speed counters. However,I have tried to use through wizard but I couldn't. So I need a program that really show how I can use HSC properly. Another problem, if it is possible to use one input of PLC (ex. I0.0) as an input interrupt, instead of input interrupt counter. Thanks for your concern. my e-mail: [email protected], you can send program to my e-mail.