Manual

Chapter 1
Planning for a Protected System
1-2
To control: Enhanced PLC-5 processors let you:
In addition, protected processors
let you use DTEP to:
I/O Forcing
Allow or disallow the I/O-Force privilege
for a class of users
Gives only total or no control
Prevent modification of specific
module groups by I/O forcing
initiated by an end user
Data-Table Write
 Allow or disallow the Logical-Write
privilege for a class of users
Gives only total or no control
 Set read-only protection on
particular files
Neither mechanism prevents any user
from writing logic that bypasses the
protections in order to modify a specific
data-table location
Prevent writes to specific segments
of data-table words by:
 sending write commands directly
to the data table
 adding or modifying ladder
instructions that can write to the
protected area
Hardware Required Software Required
PLC-5/26, -5/46, or -5/86 Programmable Controller
(1785-L26B, -L46B, or -L86B; Series C, Revision G or later)
6200 Series PLC-5 Programming
Software, Release 5.0 or later
After you finish designing a PLC-5 protected-processor system, your primary
role as system administrator becomes preventing end users from defeating
whatever security mechanisms you designed into the system.
Main Design of System Complete
System Administrator Determines Which Privileged Areas Require Protection
What classes of users need to be accommodated?
Which features do they need to access?
System Administrator Identifies Which Portions of Memory Require Protection
In what areas of which data or program files would alterations interfere with the intended operation?
System Administrator Sets Up and Tests
Passwords and privileges
DTEP mechanism
System Administrator Turns System Over to End User
Keeps privilege to modify privileges
Requirements
Implementation Guidelines