| HeaderByte1 | SEL Fast message data frame header byte 1. |
| HeaderByte2 | SEL Fast message data frame header byte 2. |
| MaximumAnalogValues | Absolute maximum number of possible analog values that could fit into a data frame. |
| MaximumDataLength | Absolute maximum data length (in bytes) that could fit into any frame. |
| MaximumDigitalValues | Absolute maximum number of possible digital values that could fit into a data frame. |
| MaximumExtendedDataLength | Absolute maximum number of bytes of extended data that could fit into a command frame. |
| MaximumPhasorValues | Absolute maximum number of possible phasor values that could fit into a data frame. |