135
Holding Area (H)
Section 4-6
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.)
4-6
Holding Area (H)
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.
Holding Area Initialization
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).
Self-maintaining Bits
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.
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.
Precautions
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
H0.00
Input
Unit
Set input
Reset input
H1.00
Summary of Contents for CP1L - 12-2007
Page 3: ...iv...
Page 9: ...x...
Page 13: ...xiv TABLE OF CONTENTS...
Page 21: ...xxii...
Page 33: ...xxxiv Conformance to EC Directives 6...
Page 65: ...32 Function Blocks Section 1 5...
Page 428: ...395 Clock Section 6 9...
Page 429: ...396 Clock Section 6 9...
Page 523: ...488 Troubleshooting Unit Errors Section 9 4...
Page 531: ...496 Replacing User serviceable Parts Section 10 2...
Page 563: ...528 Auxiliary Area Allocations by Function Appendix C...
Page 611: ...576 Auxiliary Area Allocations by Address Appendix D...
Page 638: ...603 Connections to Serial Communications Option Boards Appendix F Connecting to Unit...
Page 639: ...604 Connections to Serial Communications Option Boards Appendix F...
Page 669: ...634 Index...
Page 671: ...636 Revision History...