Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Interrupt nesting in Mitsubishi FX1N

Interrupt nesting in Mitsubishi FX1N

Interrupt nesting in Mitsubishi FX1N

Being recently involved in debugging of FX1N program
with massive interrupts, I have performed some simple
programming tests to clarify for myself the FX1N
behavior in sense of interrupts nesting and lost interrupts.
Some of the results are unexpected.

Test 1.
High-speed pulse output Y0 is connected directly to the
high-speed input with interrupt assigned.
Y0 generates known number of pulses and the test is performed with different Y0 frequencies.
A data register increment is performed in the interrupt in order to monitor the number of interrupt executions.
Test result: after some frequency of Y0, some of the interrupts are lost.
This is an expected and obvious result.
Note: there is no any indication of lost interrupts in the PLC devices.

Test 2.
Same as test 1, but Y0 is connected to two high-speed inputs, resulting in simultaneous request of two interrupts.
A data register increment is performed in each interrupt in order to monitor the number of each interrupt executions.
Test result: after some frequency of Y0 some of the lower priority interrupts are lost, while the interrupt with higher priority is still performed on each pulse.
Conclusion: after simultaneous request an interrupt with lower priority waits to be executed, but not in "first come first served" line. If another higher priority interrupt occurs, this lower priority interrupt waits again and may be lost.
This is an expected, but not an obvious result.

Test 3.
Same as test 1, but in the interrupt body another output (Y1) is set, refreshed, reset and refreshed again.
In another words, interrupt generates short Y1 pulse strictly during its execution.
Y1 is connected to another high-speed input with another interrupt assigned.
This second interrupt increments two registers: one same as in the previous tests and another increment is under Y1 condition in order to indicate the second interrupt execution during Y1 pulse (meaning interrupt nesting).
The result: nesting never detected. Both interrupts increment registers, but the conditional
increment in the second interrupt is never performed.
This means the second interrupt still waiting instead of being nested !?

Test 3 was performed with and without enabling interrupts within the interrupts bodies.
Also the interrupt priorities were exchanged.
All with the same result.

This is totally unexpected.
Can anybody explain me this ?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close