Chapter 4. Ladder Diagram (LD) Programming
100 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C
PTCON and NTCON
Warning
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.
Positive Transition Contact PTCON
Negative Transition Contact NTCON
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
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
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
The variable associated with
PTCON or NTCON contact
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.
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