Online Editing With PLC in Run Mode
The ladder logic program may be edited while the PLC is in the Run mode. A few more steps are required, since accepted rungs are not immediately executed. The process of online editing is illustrated by Figure 1. After rungs are edited, they must be tested and then assembled before the process is complete. If the edits are discovered to be unacceptable while in the "Test Edit" mode, the edits may be untested and modified, or cancelled.
While online editing a rung (edit, insert, replace, or delete), edit zone markers are placed in the left margin. These indications are explained below. While a rung is being edited, the zone markers are lower case, indicating that the edited rung exists only in the computer memory, not in the PLC. After a rung is accepted, the edit zone markers change to upper case letters, indicating that the edited rung is now in the PLC, but not being executed. Other rungs may be edited. After edited rungs are accepted, the old (R and D edit zones) and new rungs (I edit zones) co-exist in the PLC. However, only the old rungs are executed. The new rungs are skipped, indicated by the edit zone markers in the left margin.
To execute the new rungs, the edits must be tested (right mouse, Test Edits). While the edits are being tested, the new rungs (I edit zones) are executed and the old rungs (R and D edit zones) are skipped.
If the program operation with the new rungs is acceptable, then the new rungs should be assembled (right mouse, Assemble Edits). When the rungs are assembled, the old rungs are deleted from the PLC memory and the edit zone markers are removed.
If the new rungs are unacceptable, then the new rungs should be untested (right mouse, Untest Edits). When the rungs are untested, rungs are restored to their state before the rungs were tested. The old rungs (R and D zones) are executed and the new rungs (I zones) are skipped.
After the rungs have been untested, or before the edits are tested, the edits may be cancelled (right mouse, Cancel Edits). When the edits are cancelled, the new rungs (I zones) are deleted and the edit zone markers are removed.
Lower-case edit zone markers
e) (Offline and online) These rungs are currently being edited and are contained in the computer memory. If one is working offline, the edit zone marker disappears after the rung is successfully verified (right mouse button selection). If one is working online, the edit zone marker is changed to an upper-case I after the rung is successfully accepted (right mouse button selection).
i) (Online) These rungs will be inserted into the PLC program, but exist in the computer memory, not in the PLC memory. After the rung is successfully accepted (right mouse button selection) the rung is inserted into the PLC memory and the edit zone marker is changed to an upper-case I.
r) (Online) These rungs will be replaced in the PLC program. An r marked rung is always preceded by an e marked rung. After the e marked rung is successfully accepted (right mouse button selection) the r edit zone marker is changed to a R edit zone.
d) (Online) These rungs will be deleted from the PLC program. However, the lowercase d indicates that the deletion only exists in the computer memory. When the rung is accepted (right mouse button selection), the lower-case d is replaced by an upper-case D, indicating that the deletion exists in the PLC memory.
Upper-case edit zone markers
I) (Online) These rungs are inserted into the PLC program. To test the rung execution, select "Test Edits" (right mouse button selection). Select "Assemble Edits" to finalize rung insertion and to remove the edit zone markers.
R) (Online) These rungs are replaced in the PLC program. However, an R marked rung is still executed until "Test Edits" is selected. When "Assemble Rungs" is selected, the rung is deleted.
D) (Online) These rungs are deleted from the PLC program. However, a D marked rung is still executed until "Test Edits" is selected. When "Assemble Rungs" is selected, the rung is deleted.
While online editing a rung (edit, insert, replace, or delete), edit zone markers are placed in the left margin. These indications are explained below. While a rung is being edited, the zone markers are lower case, indicating that the edited rung exists only in the computer memory, not in the PLC. After a rung is accepted, the edit zone markers change to upper case letters, indicating that the edited rung is now in the PLC, but not being executed. Other rungs may be edited. After edited rungs are accepted, the old (R and D edit zones) and new rungs (I edit zones) co-exist in the PLC. However, only the old rungs are executed. The new rungs are skipped, indicated by the edit zone markers in the left margin.
To execute the new rungs, the edits must be tested (right mouse, Test Edits). While the edits are being tested, the new rungs (I edit zones) are executed and the old rungs (R and D edit zones) are skipped.
If the program operation with the new rungs is acceptable, then the new rungs should be assembled (right mouse, Assemble Edits). When the rungs are assembled, the old rungs are deleted from the PLC memory and the edit zone markers are removed.
If the new rungs are unacceptable, then the new rungs should be untested (right mouse, Untest Edits). When the rungs are untested, rungs are restored to their state before the rungs were tested. The old rungs (R and D zones) are executed and the new rungs (I zones) are skipped.
After the rungs have been untested, or before the edits are tested, the edits may be cancelled (right mouse, Cancel Edits). When the edits are cancelled, the new rungs (I zones) are deleted and the edit zone markers are removed.
Lower-case edit zone markers
e) (Offline and online) These rungs are currently being edited and are contained in the computer memory. If one is working offline, the edit zone marker disappears after the rung is successfully verified (right mouse button selection). If one is working online, the edit zone marker is changed to an upper-case I after the rung is successfully accepted (right mouse button selection).
i) (Online) These rungs will be inserted into the PLC program, but exist in the computer memory, not in the PLC memory. After the rung is successfully accepted (right mouse button selection) the rung is inserted into the PLC memory and the edit zone marker is changed to an upper-case I.
r) (Online) These rungs will be replaced in the PLC program. An r marked rung is always preceded by an e marked rung. After the e marked rung is successfully accepted (right mouse button selection) the r edit zone marker is changed to a R edit zone.
d) (Online) These rungs will be deleted from the PLC program. However, the lowercase d indicates that the deletion only exists in the computer memory. When the rung is accepted (right mouse button selection), the lower-case d is replaced by an upper-case D, indicating that the deletion exists in the PLC memory.
Upper-case edit zone markers
I) (Online) These rungs are inserted into the PLC program. To test the rung execution, select "Test Edits" (right mouse button selection). Select "Assemble Edits" to finalize rung insertion and to remove the edit zone markers.
R) (Online) These rungs are replaced in the PLC program. However, an R marked rung is still executed until "Test Edits" is selected. When "Assemble Rungs" is selected, the rung is deleted.
D) (Online) These rungs are deleted from the PLC program. However, a D marked rung is still executed until "Test Edits" is selected. When "Assemble Rungs" is selected, the rung is deleted.
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