We will go into more detail about this in our 'What makes a TON timer tick' article but we hope this is enough to convince you that there are no additional mysterious steps for a PLC to properly track the accumulated value of a timer. Observe that our mystery bits in N7:5 are now in sync with our T4:0 accumulated value. Rockwell Installation Manual for RSLogix 500 includes this information. Now with I:0/0 ON, switch the PLC to 'Program' mode and then back to 'Run' mode. Rslogix 500 Software CostIts buried somewhere in the Rockwell downloads page. assigning symbols to the I/O channels The second step is not absolutely necessary, but it is easier to specify symbols now than when programming the ladder logic. Each time you enable it, our mystery value is different.ĥ. Using the RSLogix software, configuration of the inputs and outputs involves two steps: 1. Note that our mystery N7:5 word changes along with the accumulated value although their values are probably not the same. Also we have placed S2:4, the free running clock's value the instant the timer was enabled in N7:4.Ĥ. To study these mystery bits further, we have copied T4:0 to N7:0 and additionally have masked the known bits, 13, 14, and 15 and placed the remainder in N7:5. That only accounts for 3 or the 16 bits of that word.ģ. But the other word only identifies the EN (Enable), TT (Timer Timing), and DN (Done) bits. You see the the ACC (Accumulated) and PRE (Preset) take up a word each (16 bits each). That means each timer consumes 3 words.Ģ. You can see we have 40 elements that take up 120 words. On the left hand pane, right click the 'Data Files' folder and select properties. One reason we chose the Micrologix 1000 for this project is it allows the copying of the T4 data table to the N7 data table.ġ. 01, it never made sense to me how the TON instruction could keep track of 32767 seconds when it has a time base of 1 second. While it is feasible for the processor to be able to update the TON's accumulated value when the timebase is. As you read more of our lessons you will find that we don't believe there are any mysteries to how a PLC functions. Most explanations of timers end with the explanations contained in the rungs above, leaving the timers internal operation somewhat of a mystery.

Manual rslogix 500