147
Overview of I/O Memory Area
Section 4-1
Note *The following areas of I/O memory will be cleared during mode changes
(between PROGRAM and RUN/MONITOR) unless the IOM Hold Bit is ON:
the CIO Area (I/O Area, Data Link Area, CPU Bus Unit Area, Special I/O Unit
Area, DeviceNet (CompoBus/D) Area, and Internal I/O Areas), Work Area,
Timer Completion Flags, and Timer PVs.
Auxiliary Area Flags and Words
When the IOM Hold Bit is ON, all outputs from Output Units will be maintained
when program execution stops. When the program starts again, outputs will
have the same status that they had before the program was stopped and
instructions will be executed. (When the IOM Hold Bit is OFF, instructions will
be executed after the outputs have been cleared.)
PLC Power ON
In order for all data* in I/O memory to be retained when the PLC is turned ON,
the IOM Hold Bit must be ON and it must be protected in the PLC Setup using
the IOM Hold Bit Status at Startup parameter.
Auxiliary Area Flags and Words
PLC Setup
Name
Address
Description
IOM Hold Bit
A500.12
Specifies whether the I/O memory will be retained or not
when the CPU Unit operating mode is changed
(between PROGRAM and RUN/MONITOR) or when the
power is cycled.
OFF: I/O memory is cleared to 0 when the operating
mode is changed.
ON:
I/O memory is retained when the operating mode
is changed between PROGRAM and RUN or
MONITOR.
Name
Address
Description
IOM Hold Bit
A500.12
Specifies whether the I/O memory will be retained or
not when the CPU Unit operating mode is changed
(between PROGRAM and RUN/MONITOR) or when
the power is cycled.
OFF: I/O memory is cleared to 0 when the operating
mode is changed.
ON:
I/O memory is retained when the operating
mode is changed between PROGRAM and
RUN or MONITOR.
Name
Description
Setting
Default
IOM Hold
Bit Status
at Startup
To retain all data in I/O
memory when the PLC
is turned ON, set the
IOM Hold Bit at startup
parameter to hold the
status of the I/O Hold Bit.
OFF:
The IOM Hold Bit is cleared
to 0 when power is cycled.
ON:
The status of the IOM Hold
Bit is retained when power is
cycled.
OFF
(Cleared)
Retained
Power ON
I/O memory
CIO and
other areas
Summary of Contents for CP1H-CPU - 05-2006
Page 2: ...CP1H X40D CP1H XA40D CP1H Y20DT D CP1H CPU Unit Operation Manual Revised May 2006...
Page 3: ...iv...
Page 11: ...xii TABLE OF CONTENTS...
Page 15: ...xvi...
Page 19: ...xx...
Page 31: ...xxxii Conformance to EC Directives 6...
Page 71: ...40 Function Blocks Section 1 5...
Page 133: ...102 Computing the Cycle Time Section 2 7...
Page 169: ...138 CPM1A Expansion I O Unit Wiring Section 3 6...
Page 411: ...380 Clock Section 6 8...
Page 519: ...488 Replacing User serviceable Parts Section 10 2...
Page 527: ...496 Standard Models Appendix A...
Page 535: ...504 Dimensions Diagrams Appendix B...
Page 628: ...597 Connections to Serial Communications Option Boards Appendix F Connecting to Unit...
Page 629: ...598 Connections to Serial Communications Option Boards Appendix F...
Page 659: ...628 PLC Setup Appendix G...
Page 665: ...634 Index work words 159 write protection 370...
Page 667: ...636 Revision History...