Holding Area (H) - Omron CP1L Operation Manual

Holding Area (H)

4-6 Holding Area (H)
Holding Area Initialization
Self-maintaining Bits
Precautions
154
4. When PLC operation is stopped when a fatal error other than an
FALS(007) error occurs. (The contents of the Work Area will be retained
when FALS(007) is executed.)
The Holding Area contains 512 words with addresses ranging from H0 to
H511 (bits H0.00 to H511.15). These words can be used in programming.
Data in the Holding Area is not cleared when the power is cycled or the PLC's
operating mode is changed from PROGRAM mode to RUN or MONITOR
mode or vice-versa.
A Holding Area bit will be cleared if it is programmed between IL(002) and
ILC(003) and the execution condition for IL(002) is OFF. To keep a bit ON
even when the execution condition for IL(002) is OFF, turn ON the bit with the
SET instruction just before IL(002).
When a self-maintaining bit is programmed with a Holding Area bit, the self-
maintaining bit won't be cleared even when the power is reset.
Note 1. If a Holding Area bit is not used for the self-maintaining bit, the bit will be
turned OFF and the self-maintaining bit will be cleared when the power is
reset.
2. If a Holding Area bit is used but not programmed as a self-maintaining bit
as in the following diagram, the bit will be turned OFF by execution condi-
tion A when the power is reset.
H0.00
3. H512 to H1535 are used as a Function Block Holding Area. These words
can be used only for function block instances (internally allocated variable
area). These words cannot be specified as instruction operands in the user
program.
When a Holding Area bit is used in a KEEP(011) instruction, never use a nor-
mally closed condition for the reset input if the input device uses an AC power
supply. When the power supply goes OFF or is temporarily interrupted, the
input will go OFF before the PLC's internal power supply and the Holding Area
bit will be reset.
H0.00
H0.00
A
Input
Unit
Section 4-6
Set input
H1.00
Reset input