CALL NOWCALL NOWCALL NOWGATEWAY SELECTORCALL NOWGATEWAY SELECTORLEARN MORELEARN MORE PROCEED TO CHECK-OUT SUBSCRIBE TO OUR RSS FEED SEARCH GATEWAYS NOW SEND MESSAGE NEWSLETTER | SUBSCRIBESUBMIT CALL NOWCALL NOWCALL NOWGATEWAY SELECTORCALL NOWGATEWAY SELECTORLEARN MORELEARN MORE PROCEED TO CHECK-OUT SUBSCRIBE TO OUR RSS FEED SEARCH GATEWAYS NOW SEND MESSAGE NEWSLETTER | SUBSCRIBESUBMIT

BACnetMSTP - How often should a BACnet MSTP device search for a new master

A BACnet MSTP device should search for a new master after it has gotten the token more then Npoll – 1 times.
If your device is on a large network (20+ nodes), and Npoll is set to a very high number, it may take a long time for your device to find a new device between its own MAC address and its next station.

For example,

There are three devices on the network, 0x02, 0x03, 0x07.
All of the devices have a Npoll of 255, and have received the token 254 times since the start.

0x02 receives the token and increments its own TokenCount to 255. 0x02 now goes in to poll for master mode and attempts to find a new master, the NS (next station) just happens to be the PS (poll station) as well, so TokenCount is reset to zero without a poll for master message being sent out. 0x02 sends the token to 0x03.

0x03 receives the token and increments its own TokenCount to 255. 0x03 now goes in to poll for master mode and attempts to find a new master. It will poll for a new master between the range of 0x04-0x06. If it does not find a new master, it will pass the token on to 0x07.

0x07 receives the token and increments its own TokenCount to 255. 0x03 now goes in to poll for master mode and attempts to find a new master. It will poll for a new master between the range of 0x08-Nmax_master, then 0x00-0x01. But 0x07 has a Nmax_info_frames of 5 so it will only poll for 5 new master before it will pass on the token to 0x02. Next time 0x07 receives the token, it will start to poll for a new master where it last left off at 5 frames a time.

Npoll
The number of tokens received or used before a Poll For Master cycle is executed: Default: 50.

Nmax_master
This parameter represents the value of the Max_Master property of the node's Device object. The value of Max_Master specifies the highest allowable address for master nodes. The value of Max_Master shall be less than or equal to 127. If Max_Master is not writable in a node, its value shall be 127.

Nmax_info_frames
This parameter represents the value of the Max_Info_Frames property of the node's Device object. The value of Max_Info_Frames specifies the maximum number of information frames the node may send before it must pass the token. Max_Info_Frames may have different values on different nodes. This may be used to allocate more or less of the available link bandwidth to particular nodes. If Max_Info_Frames is not writable in a node, its value shall be 1.

Gateway Selector

Select your combination of protocols.
Protocol 1
Protocol 2

Contact Us

Contact us via phone (+1 866-383-1657) or leave a detailed message below for sales, support, or any other needs

*Required Field
I'd like to receive the newsletter. *Check email for confirmation.
*Required Field
Preferred Time To Be Contacted (PST)
8:00am - 12:00pm 12:00pm - 5:00pm