Example calculation of required router memory

The example below shows a calculation of the required router memory.

Example requirement:

280 digital and analog objects = 280 x 20 KB = 5,600 KB

280 Trendlog = 280 x 20 KB = 5,600 KB (properties only)

Trendlog buffer size (7 days / 10 min. interval) = 1440 / 10 * 7 = 1008 records per Trendlog

Memory requirement for Trendlog buffer: 280 * 1008 * 56 = 15,805,440 (56 bytes per data record in log memory)

Total Router Memory required

5,600,000 bytes normal objects

5,600,000 bytes Trendlog objects

15,805,440 bytes Trendlog buffer

Total Router memory for BACnet

27,005,440 bytes

Please note that the total BACnet router memory is only 60 % of the total required router memory, so the default value of 32 MB would not be sufficient for this example and must be increased.

The amount of router memory can be specified in the Real-Time settings of TwinCAT. Please note, that the router memory will be assigned after restarting the controller.