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86 Mentor MP User Guide
www.controltechniques.com Issue: 3
10 Onboard PLC
10.1 Onboard PLC and SYPT Lite
The Mentor MP has the ability to store and execute a 6kB Onboard PLC
ladder logic program without the need for additional hardware in the form
of a Solutions Module.
The ladder logic program is written using SYPT Lite, a Windows™
based ladder diagram editor allowing the development of programs for
execution in SM-Applications Plus.
Advantages of SYPT Lite:
• SYPT Lite is designed to be easy to use and to make program
development as simple as possible. The features provided are a
sub-set of those in the SYPT program editor.
• SYPT Lite programs are developed using ladder logic, a graphical
language widely used to program PLCs (IEC 61131-3).
• SYPT Lite allows the user to draw a ladder diagram representing a
program.
• SYPT Lite provides a complete environment for the development of
ladder diagrams. Ladder diagrams can be created, compiled into
user programs and downloaded to SM-Applications Plus for
execution, via the RJ45 serial communications port on the front of
the drive.
• The run-time operation of the compiled ladder diagram on the target
can also be monitored using SYPT Lite and facilities are provided to
interact with the program on the target by setting new values for
target parameters.
• SYPT Lite is available on the CD that is supplied with the drive.
10.2 Benefits
The combination of the Onboard PLC and SYPT Lite means that Mentor
MP can replace nano and some micro PLCs in many applications. The
Onboard PLC programs can consist of up to a maximum of 50 ladder
logic rungs (up to 7 function blocks and 10 contacts per rung). The
Onboard PLC program can also be transferred to and from a
SMARTCARD for backup or quick commissioning / start-up.
In addition to the basic ladder symbols, SYPT Lite contains a sub-set of
the function from the full version of SYPT. These include:
• Arithmetic blocks
• Comparison blocks
•Timers
• Counters
• Multiplexers
•Latches
• Bit manipulation
Typical applications for the Onboard PLC include,
• Ancillary pumps
• Fans and control valves
• Interlocking logic
• Sequences routines
• Custom control words.
10.3 Limitations
Compared with the SM-Applications Plus or SM-Applications Lite V2
modules when programmed with SYPT, the Onboard PLC program has
the following limitations:
• The maximum program size is 6080 bytes including header and
optional source code.
• The Mentor MP is rated for 100 program downloads. This limitation
is imposed by the flash memory used to store the program within the
drive.
• The user cannot create user variables. The user is only able to
manipulate the drive parameter set.
• The program cannot be downloaded or monitored over CTNet. The
program is only accessible via the drives RJ45 serial
communications port.
• There are no real-time tasks, i.e. the scheduling rate of the program
cannot be guaranteed. SM-Applications Plus tasks such as Clock,
Event, Pos0 or Speed are not available.
• The Onboard PLC should not be used for time-critical applications.
For time-critical applications either the SM-Applications Plus or SM-
Applications Lite V2 Solutions Modules should be used.
The program runs at a low priority. The Mentor MP provides a single
background task in which to run a ladder diagram. The drive is prioritized
to perform its major functions first, e.g. motor control, and will use any
remaining processing time to execute the ladder diagram as a
background activity. As the drive's processor becomes more heavily
loaded, less time is spent executing the program.
Figure 10-1 Mentor MP Onboard PLC program scheduling
The user program is scheduled for a short period approximately once
every 64ms. The time for which the program is scheduled will vary
between 0.2ms and 2ms depending on the loading of the drive's
processor.
When scheduled, several scans of the user program may be performed.
Some scans may execute in microseconds. However, when the main
drive functions are scheduled there will be a pause in the execution of
the program causing some scans to take many milliseconds. SYPT Lite
displays the average execution time calculated over the last 10 scans of
the user program.
The Onboard PLC and SYPT Lite form the first level of functionality in a
range of programmable options for Mentor MP.
• SYPT Lite can be used with either the Onboard PLC or with SM-
Applications Lite V2 to create ladder logic programs.
• SYPT can be used with either the SM-Applications Lite V2 or SM-
Applications Plus to create fully flexible programs using ladder logic,
function blocks or DPL script.
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