1. Siemens 840D PLC user alarm number is calculated as follows:

The user alarm starts from 700000 as it corresponds to DB2.DBX180.0. You can quickly find the alarm point in the DB data block by doing the following.

180 (initial alarm point) + (middle two digits multiplied by 8) + (quotient of last two digits divided by 8 + decimal point + remainder)

Example: Alarm number 701661

180 (initial alarm point) + 16 * 8 (the middle two digits multiplied by 8, hexadecimal algorithm) + 61/8 (the last two digits divided by 8 = quotient plus decimal point + remainder, than so for the quotient of 7 remainder 5) = 180 + 128 + 7.5 = 315.5, so the alarm bit of the 701661 for DB2.DBX315.5.



2. Siemens 828D provides 248 PLC user alarms

(700000 - 700247), the corresponding interface signal is DB1600.DBX0.0 - DB1600.DBX30.7.

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