With “drivewait” designation in “seqtable” statement, after the periodic start type sequence ta- ble block (TE type or TC type) of the designated tag name is one-shot periodically started, the sequence table block mode changes to AUT, and the program waits for an SFC/SEBOL re- turn event message to be output from the sequence table block.
Except for that the program waits for the message output from the sequence table block, the “drivewait” designation operates in the same way as the “drive” designation.
The format of “drivewait” designation in “seqtable” statement is shown below:
<5.15 Sequence Table (ST16, ST16E) Block Operation>
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seqtable drivewait <tag name> [, <execution step name>]; <action signal column parameter>
[;<error variable>] [; error <label> [,<error identifier>] ]
errorsub
<tag name> Designate a tag name. A local generic name and dummy argument function
block can also be designated.
<execution step name> Designate the step name for a step-type sequence table with
a character-string constant or character-string variable of two bytes or less. If the character string is longer than two bytes, the first two bytes are used. <action signal column parameter>
Designates a long-type local variable to which the parameter for the sequence table action signal column
(SFC/SEBOL return event message, %RE) will be returned.
<error variable> Designate the local variable to which the error code is set.
If no error occurs, this is set to 0.
<label> Designate the branching destination at the time an error occurs.
<error identifier> Designate a local variable or a constant to identify where the error was
generated in the error handling section.
Figure 5.15-4 The format of the "seqtable” statement with “drivewait” designation
In the case of step type sequence table block, when the <execution step name> is designa- ted, the step is changed to <execution step name> prior to the one shot execution. After the designated step and the [00] step are executed in one shot, the sequence table block is peri- odically started.
If the step in the <execution step name> does not exist, a run-time error occurs. In this case the sequence table block is not executed and the block mode does not change.
If an <execution step name> is not designated, the step of the PV value held by the sequence table at that point and the [00] step are executed as a one-shot, then that sequence table block is periodically executed from that step.
If the sequence table block is a non-step type, all rules are executed. Even if an <execution step name> is designated in a non-step type sequence table, it will be disregarded.
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SFC/SEBOL Return Event Message for “drivewait” Designation in
“seqtable” Statement
With “drivewait” designation in “seqtable” statement, the parameter designated in the se- quence table block’s action signal column is returned to <action signal column parameter> when an SFC/SEBOL return event message is output from the sequence table block. Be- cause the parameter value is in the range of 0 to 65535, designate a long-type local variable
More precisely, the timing that the sequence table block automatically changes its mode from AUT to MAN is the moment that the SFC block is forced to terminate by a block status change command while the sequence table block started by “drivewait” statement is in AUT mode, and right before SFC/SEBOL return message is output.
When a one-shot execution is performed for the first time, if that sequence table block outputs an SFC/SEBOL return event message, the block mode becomes MAN and a periodic start will not be executed after that.
When the block mode of the sequence table block is AUT and it has already been executed periodically, an error does not occur even if the “seqtable” statement is executed. The se- quence table block is executed as a one-shot and will continue to be started periodically.
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Periodic Start
If the block mode of a periodic start type sequence table block (TE type or TC type) is
changed to AUT, the sequence table block will be periodically started from the next operation timing.
The expression when the block mode of the sequence table block is changed to AUT is shown below:
<tag name>. MODE= "AUT"
Figure 5.15-5 The format when changing the block mode of the sequence table (ST16) block to AUT.
To perform periodic start of the sequence table block with error check, use a group assign- ment statement.
With “drive” designation in “seqtable” statement, the sequence table block will first be execu- ted as one-shot during the execution of the “seqtable” statement. However, if the block mode is changed to AUT, execution begins from the sequence table block’s next operation timing. The sequence table block is started by changing the block mode when starting sequence ta- ble blocks in another FCS or when one-shot execution is not desirable. When start the se- quence table block in other control stations, if the one-shot start is not required, the block may be started by changing the block mode.
SEE
ALSO For more information about group assignment statement, refer to: 5.2, “Group Assignment Statement” on page 5-10
<5.15 Sequence Table (ST16, ST16E) Block Operation>
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5.16
Logic Chart Block (LC64, LC64-E)
Operation
In SEBOL, one-shot execution, periodic start with one-shot execution and periodic start may be applied to Logic Chart Block.
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Logic Chart Operation Using a “logicchart” Statement
A logic chart block can perform one-shot execution when the block mode is either MAN or AUT. The block mode does not change even after a one-shot execution has been performed. However, the operation that include oneshot execution may be only applied to the logic chart within the same FCS.
Table 5.16-1 Table Logic Chart Blocks Operated with “logicchart” Statement
Operation type(*1)T type(*1)O type(*1)B/I Control other sta-tions(*1)
One-shot execution x x x -
Periodic start with one-shot execution x - - -
Periodic start (Change block mode to AUT) x Δ Δ x
*1: x: Operation allowed -: Run-time error
Δ: Block mode changes to AUT, but periodic start is not performed.
Types for logic chart block processing timing are shown as follows: T: Periodic start, and output only when condition establishes
O: One-shot start, and output every scan when condition establishes B: Execute once after initial cold start
I: Execute once after initial cold start or after restart caused by momentary power failure Logic chart block with processing timing of B type or I type is originally provided for running the user defined initialization processing when the FCS executes an initial cold start or restart. However, the logic chart blocks may also be activated by a SEBOL “logicchart” statement. In this case, please be noted that the block will perform a one-shot execution at the timing that the SEBOL statement is executed.
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One-Shot Execution
When the “logicchart” statement is designated as a one-shot execution command, the logic chart block with the designated tag name will be executed for a one-shot. If it the result of condition check indicates that the condition is satisfied, status manipulation will be executed. The format for one-shot execution is given as below.
logicchart oneshot <tag name>
[;<error variable>] [; error <label> [,<error identifier>] ]
errorsub
<tag name> Designate a tag name. A local generic name and dummy argument function block
can also be designated.
<error variable> Designate the local variable to which the error code is set. If no error occurs,
this is set to 0.
<label> Designate the branching destination at the time an error occurs.
<error identifier> Designate a local variable or a constant to identify where the error was generated in the error handling section.
Figure 5.16-1 The format of the “logicchart” statement with “oneshot” designation
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Periodic Start with One-Shot Execution
There are two methods to perform periodic start with one-shot execution for logic chart block by “logicchart” statement with “drive” designation or by “logicchart” statement with “drivewait” designation.