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Chapter 4. Ladder Diagram (LD) Programming
Operands for POSCOIL and NEGCOIL
Parameter Description
BOOL_V
The variable associated with
POSCOIL or NEGCOIL
Example for POSCOIL and NEGCOIL
When reference E1 goes from OFF to ON, coils E2 and E3 receive power flow, turning E2 ON. When
E1 goes from ON to OFF, power flow is removed from E2 and E3, turning coil E3 ON.
PTCOIL and NTCOIL
Because the behavior of PTCOILs and NTCOILs is determined only by the current power flow into the
coil and the previous power flow into the coil (i.e., the transition bit), it is not affected by writes to its
associated BOOL variable by other coils or instructions in the logic. Therefore, many of the cautions
that apply to POSCOILs and NEGCOILs do not apply to PTCOILs and NTCOILs.
88
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
Allowed Operands
BOOL variable: I, Q, M, T, G, SA, SB, SC, symbolic
discrete variables, and I/O variable.
Bit reference in BOOL variable: I, Q, M, T, G, SA, SB,
SC
PTCOIL and NTCOIL instructions should not be used in a
■
parameterized block or user-defined function block (UDFB)
with a parameter or member. In these cases, an R_TRIG or
F_TRIG should be used instead.
The transition bit of a given PTCOIL or NTCOIL is changed
■
only once per CPU scan. Therefore, using a PTCOIL or
NTCOIL in a block that can be called multiple times per
scan can have adverse effects on all calls after the first one
because the PTCOIL or NTCOIL cannot detect the
transition on the second and subsequent calls.
Do not override a transition coil by putting a force on its
■
reference bit. If a transition coil is overridden, the coil has
no effect on the bit, and if the override is then removed,
the coil might be set ON for one sweep. . This can cause
unexpected consequences in the Controller logic and in
field devices attached to the Controller.
Do not use a transition contact with the same reference
■
address used on a transition coil because the value of the
transition bit, which stores the power flow value into the
coil, will be affected.
Warning
Optional
No
GFK-2950C
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