trailing/leading/pulse output

[bigjoe]

I am just in the beginner level on PLC and I am using FX plc and I am using the manuals from this site, somehow I think those manuals are for pro's who already have a deeper knowledge. When I read the instruction about the trailing/falling and pulse output I don't fully understand them. So anybody can help? explain and give some examples? johnny

[Goody]

Depending on the CPU (and the FX doesnt support -|P|-) the action is done either immediately the signal is present for one scan - or is done when the signal is lost. (for one scan.) In the FX instead of using rising or falling bits you would use -[PLS M0] or -[PLF M0] A typical example of using a rising edge signal would be that the signal is likely to be on longer than you would want a subsequent action to be on for. Using PLS or -[P] you can latch another circuit but unlatch it by other methods reguardless of whether the original signal is still there or not.

[Sergei Troizky]

In Mitsubishi terms "pulse" applies to bit being On one PLC scan long. The PLS instruction generates a pulse when the condition becomes true. The PLF instruction generates a pulse when the condition becomes false. The pulse bit is On until this instruction is read again in the next scan. So called "pulse format" of the applied instruction allows to execute the instruction only once when the condition becomes true. Then it will not be executed as long as the condition remains true. This format is created by suffixing the instruction with "P" and is supported by FX. Edited July 3, 2005 by Sergei Troizky

[bigjoe]

hi guys, thanks for your time and knowledge. johnny