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Chapter 4. Ladder Diagram (LD) Programming
PTCON and NTCON
Positive Transition Contact PTCON
PTCON passes power flow to the right only when
all of the following conditions are met:
The input power flow to PTCON is ON.
■
The value of the BOOL variable associated
■
with PTCON is ON.
The transition bit associated with the PTCON
■
is OFF
The transition bit depends on the value of the BOOL variable associated with this PTCON or NTCON
when it was last executed.
Notes:
As soon as a PTCON or NTCON is set to ON or OFF, it updates its transition bit.
■
Multiple instances of PTCON and/or NTCON can be associated with the same BOOL variable, but
■
the instance data of each instance of the PTCON or NTCON associated with the BOOL variable is
unique, that is, it is tracked independently.
Transition data is non-retentive, that is, it is cleared to OFF when the CPU transitions from STOP
■
Mode to RUN Mode. As a result, the first time a PTCON executes with its input power flow set to
ON and its associated BOOL variable also set to ON, it passes power flow to the right.
Operands for PTCON and NTCON
Parameter Description
BOOL_V
The variable associated with
PTCON or NTCON contact
100
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
PTCON or NTCON instructions should not be used in a
parameterized block or user-defined function block with a
parameter or member. In these cases, an R_TRIG or F_TRIG
should be used instead.
The transition bit of a given PTCON or NTCON is updated
only once per CPU scan. Therefore, using a PTCON or
NTCON in a block that can be called multiple times per scan
may have adverse effects on all calls after the first one
because the PTCON or NTCON cannot detect the transition
on the second and subsequent calls.
Allowed Operands
BOOL variable: I, Q, M, T, S, SA, SB, SC, and G
memories, symbolic discrete variables, I/O variables.
Bit reference in non-BOOL variable: R, AI, AQ, L, P, W,
and on symbolic non-discrete variables.
Warning
Negative Transition Contact NTCON
NTCON passes power flow to the right only when
all of the following conditions are met:
The input power flow to NTCON is ON.
■
The value of the BOOL variable associated
■
with NTCON is OFF.
The transition bit associated with the NTCON
■
is ON
Optional
No
GFK-2950C
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