Rockwell Automation 1785-Lx6B,D17856.5.13 MNL. PLC-5 PROTECTED PROCESSOR - Manual (Page 26)

Chapter 3
Configuring DTE Protection
3-5
During online program editing by the end user, the protected processor
screens all communications commands that can be used to modify data-table
elements, manipulate addresses, or force I/O. If the DTEP mechanism is
enabled—i.e., the user cannot modify privileges and there is a valid DTEP
file indicated in S:63—the protected processor screens each command for
access to protected data-table areas. This process checks all ranges in the
DTEP file. If a violation is found, the request is rejected, an error
code—
Data Table Element Protection Violation —is returned,
and minor-fault bit S:17/11 is set.
Command screening occurs during online programming by an end user—
i.e., when the programming software is connected directly to the processor.
When an end user changes a processor image off line—i.e., when the
programming software is connected to a file image of the processor—
most commands cannot be directly screened by the processor for
protection violations. For offline changes, therefore, other methods
help prevent protection violations.
Data-Table Files
As system administrator, you should follow good programming practices and
initialize all data-table locations to their desired values off the processor’s
first scan flag (S:1/15). Because the DTEP file specifies only the ranges and
not the values that should be in each location, the protected processor cannot
prevent or detect any changes that are made to the values stored in the
data-table files during offline programming. When you initialize all
data-table locations to their desired values off the processor’s first scan flag,
any problems that might have occurred due to protection violations made
during offline writing to data-table locations are nullified.
I/O Force Tables
To protect the processor operation from possible I/O force operations
included in the processor image through offline programming, the protected
processors do not accept any I/O force table changes while in download
mode. The data in the I/O force tables remain unchanged. At the end
of any download to a protected processor, the I/O force tables are clear
of any forces and a warning appears on your terminal that indicates that any
forces in the archive file were not downloaded.
Insert Elements
The protected processor does screen ladder and structured-text insert-element
instructions during downloading in order to ensure that the addresses
protected by the DTEP mechanism are not reprogrammed.
Screening Commands
Protecting from
Offline Changes