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POSCON and NEGCON Example 1
Coil E2 is turned ON when the value of the variable E1 transitions
from OFF to ON. It stays ON until E1 is written to again, causing the
POSCON to stop passing power flow.
Coil E4 is turned ON when the value of the variable E3 transitions
from ON to OFF. It stays ON until E3 is written to again, causing the
NEGCON to stop passing power flow.
POSCON and NEGCON Example 2
Bit %M00017 is set by a BIT_SET function and then cleared by a
BIT_CLR function. The positive transition contact X1 activates
the BIT_SET, and the negative transition X2 activates the
BIT_CLR.
The positive transition associated with bit %M00017 will be on
until %M00017 is reset by the BIT_CLR function. This occurs
because the bit is only written when contact X1 goes from OFF
to ON. Similarly, the negative transition associated with bit
%M00017 will be ON until %M00017 is set by the BIT_SET
function.
GFK-2950C
Chapter 4. Ladder Diagram (LD) Programming
February 2018
99
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