Token Disruptions

Overview

• Indicates the number of Reply-To-Poll-For-Master frames sent in the capture. In a stable MS/TP network, there will be Poll-for-Masters every 50 token round-trips.
• “Destination” is the device that sent the Poll-for-Master.
• The highest numbered device (last device) or the last device before a break in numbering will Poll-for-Master for all numbers up to its max Poll-for-Master limit. If you don’t have a set limit, it defaults to 127.
• If you don’t have any new devices, there will not be any responses. If you do have new devices, it will respond with “Reply-to-Poll-for-Master”.
• If a device doesn’t accept the token twice in a row (device offline or token lost because of wiring), the sender will do a Poll-for-Master to identify the next device in line.
• That device will be skipped for 50 round-trips, and then when the token comes to the break in numbers it will Poll-for-Master again. If the device is back online it will “Reply-to-Poll-for-Master”.
• Fails if you have 1 Reply-to-Poll-for-Master in the capture.

Why it fails

• Token loss due to wiring.
• The device went offline.
• The device is faulty.
• A new device was added.

How to fix it

• Look at the sources to identify the devices replying to the Poll-for-Master.
• Is it a new device you just added? If so, it’s OK.
• Check if it’s in the Unresponsive Devices list.
• Check the wiring and see if there are any problems that may be causing the device to go on and offline.

Watch us troubleshoot token disruptions in this live webinar on a shopping mall. Skip ahead to 4:00 for the token disruptions diagnostic check.