The TID is a 24 bit field in the 66 bit token data that identifies the number of minutes expired since the start of the current base date. The position of the TID is shown below in bold:
|00 ||0000 ||0101 ||110000000010101001010101 |
|0010011100010000 (1000 decimal as per amount formula in IEC62055-41) ||0001100101110000 (1970 Hex) |
With each bit of the TID field representing one minute, this gives a total duration of 16777215 minutes, or approximately 31 years. This means that the TID rolls over to zero when the one is added to the TID value at a maximum value of the TID field.