【正文】 ication specific list of required properties for selecting programmable controller was developed. There are nine criterions and the results are presented in Table 1. Selection is made by paring results table with controller’s technical data. Following is short description of every criteria involved Nature of solution determines weather it is expanding of old system or pletely new development. In first case the architecture of system and hardware requirements are limited by already existing solution. Using hardware from same pany makes servicing easier and avoids integration problems that would occur when using products form different manufacturers. For example many hardware producers integrate their own specific munication interfaces directly into processor module and for every universal protocol a special module is needed Siemens AG, 2020. It is also possible to reduce spare part stock amounts when using same type hardware all over the system imum number of electrical inputsoutputs allowed is classical criteria to determine processor class. If plex control algorithms and nonstandard functions are needed, it’s not the most important parameter any more. Generally it is money saving to use one bigger processor module for inputoutput signals that originate from nearby locations than several smaller ones. In this case there will be no need for munication work and programming will be easier tooSpecial signals and modules are usually available for medium and large controller families only. Many microcontrollers do not even have possibility to add analogue output Siemens AG, 2020. In some cases using special modules is the only way, in other ones positioning it is just an opportunity to save moneyLayouts of sensors and actuators can be very different, sometimes the sensors are located several kilometres away from the actuator pumping liquids in long pipes. In this case special munication work Profibus, ASinteface might be the only solution. If not, it can at least save costs by reducing cabling works. Not all programmable controllers have interfaces for munication protocolsProperties of processor have important role in plex applications. Most mon problem is lack of programming memory, sometimes also data memory. Memory requirements can be estimated by number of input and output signals. But in practice 100 digital inputoutput points system often has 3 times smaller program than 10 digital inputoutput points system. The only way to estimate program size exactly is using previous experienceProgram specialities include special program functions needed. Different areas of applications have some typically used functions, for example temperature control in building automation. Programming is much simpler if these functions are already built into system software of processor. In process automation 2 digital output updown closed loop PID regulation is quite often used. It might be a surprise but it’s not included in most of the microcontrollers Siemens AG, 2020 and for average programmer it’s too plicated task to create his own regulator using standard functions. Basically there are 2 solutions: either to avoid this construction or to use applicable controllerTable 1. Table for method results Communication is being more important in nowadays automation systems. In some cases nonstandardised devices as barcode readers or electronic weights have to be included into the system. Then it’s vi tal to have functions for protocol programming freeport programming