2/4/2010 11:01 AM | ||||||||||||||||||||||||||||||
Posts: 288 Rating: (22) |
Also if you want to flash the bit for counting purposes or for signalling an event, you can make use of the rising/falling edge detection instructions. the edge detection function will keep the target bit at logic "high" for one scan cycle of the OB executing the instruction from the moment the instruction detects a change in state of the bit being checked. for example, if the following STL code were to be programed as part of an OB(cyclic or not) which takes ...............say 1s for one complete execution scan, A M 0.0 FP M 0.1 = M 2.0 then M 2.0 bit would be in Logic HIGH state for 1s from the moment M 0.0 changed its state form Logic LOW to Logic HIGH and then the state of M 2.0 will return to 0, till another time the above conditions for M 0.0 repeat. if M 0.0 were to be part of the cyclic clock byte of the CPU then the above code would generate a pulse train. |
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