Posted 26 May 2016 All, I have bought a new siemens PLC 1212C. connected to TIA V13 software working perfect. When i use the clock memory byte, and selecting the 1sec bit M255.5 it is not counting. Why this is not working? What do i wrong? grtz Frans Share this post Link to post Share on other sites
Posted 27 May 2016 (edited) Did you activate it in the properties for the cpu ? Check that you don't write anything to this memory area from your code. MW254 is byte 254 and 255, and you are using MB255 for your clock. Same with MD252, it occupies 252, 253, 254 and 255. Edited 27 May 2016 by Bryll Share this post Link to post Share on other sites
Posted 27 May 2016 (edited) Hi Bryll, Thanks for the fast response. Yes i have enabled the use of the clock memory byte. I have use this feature also already with other plc's like the 314 from siemens without any problem. i have test this with a very small program with a start switch, Led, and a switch for the 1Hz clock puls M255.5 Solved the problem: After compile all the led started to flash. grtz frans Edited 28 May 2016 by Frans van Enschot 1 person likes this Share this post Link to post Share on other sites