135
Task Flags
Section 4-13
Precautions
Data Registers are normally local to each task. For example, DR0 used in
task 1 is different from DR0 used in task 2. (A PLC Setup setting can be made
from the CX-Programmer to share Data Registers between tasks.)
The content of Data Registers cannot be accessed (read or written) from the
CX-Programmer.
Do not use Data Registers until a value has been set in the register. The reg-
ister’s operation will be unreliable if they are used without setting their values.
The values in Data Registers are unpredictable at the start of an interrupt
task. When a Data Register will be used in an interrupt task, always set a
value in the Data Register before using the register in that task.
4-13 Task Flags
Task Flags range from TK00 to TK31 and correspond to cyclic tasks 0 to 31.
A Task Flag will be ON when the corresponding cyclic task is in executable
(RUN) status and OFF when the cyclic task hasn’t been executed (INI) or is in
standby (WAIT) status.
Note
These flags indicate the status of cyclic tasks only, they do not reflect the sta-
tus of interrupt tasks.
Task Flag Initialization
The Task Flags will be cleared in the following cases, regardless of the status
of the IOM Hold Bit.
1.
When the operating mode is changed from PROGRAM mode to
RUN/MONITOR mode or vice-versa
2.
When the power is cycled.
Forcing Bit Status
The Task Flags
cannot
be force-set and force-reset.
4-14 Condition Flags
These flags include the Arithmetic Flags, such as the Error Flag and Equals
Flag, which indicate the results of instruction execution.
The Condition Flags are specified with symbols, such as P_CY and P_ER,
rather than addresses. The status of these flags reflects the results of instruc-
tion execution, but the flags are read-only; they cannot be written directly from
instructions or the CX-Programmer.
Note
The CX-Programmer treats condition flags as global symbols beginning with
P_.
All Condition Flags are cleared when the program switches tasks, so the sta-
tus of the ER and AER flags are maintained only in the task in which the error
occurred.
Forcing Bit Status
The Condition Flags
cannot
be force-set and force-reset.
Summary of the Condition
Flags
The following table summarizes the functions of the Condition Flags, although
the functions of these flags will vary slightly from instruction to instruction.
Refer to the description of the instruction for complete details on the operation
of the Condition Flags for a particular instruction.
Summary of Contents for CP1L-EL20DR-D
Page 3: ...CP1L EL20D CP1L EM30D CP1L EM40D CP1L EL EM CPU Unit Operation Manual Produced July 2017...
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Page 34: ...xxxiv Software Licenses and Copyrights 7...
Page 192: ...158 Trial Operation and Debugging Section 5 3...
Page 250: ...216 Automatic Clock Adjustment and Specifying Servers by Host Name Section 6 7...
Page 666: ...632 Trouble Shooting Section 11 7...
Page 696: ...662 Standard Models Appendix A...
Page 805: ...771 Connections to Serial Communications Option Boards Appendix F Connecting to Unit...
Page 806: ...772 Connections to Serial Communications Option Boards Appendix F...
Page 836: ...802 PLC Setup Appendix G...
Page 838: ...804 TCP Status Transitions Appendix H...
Page 840: ...806 Ethernet Network Parameters Appendix I...
Page 842: ...808 Buffer Configuration CP1L EL EM Appendix J...
Page 844: ...810 Ethernet Specifications Appendix K...
Page 851: ...Index 817 work words 118 write protection 447...
Page 852: ...818 Index...
Page 854: ...820 Revision History...
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