The 5 bytes composed of the identifier and the 4 data bytes are those listed in the tables below. The identifier is the ASCII value of a letter, which are always lower than 7F and thus don't throw interrupts. The 4 data bytes are cut to 7 bit values to prevent interruptions, a 5th byte is added and contains the heavyweight-bit value for these 4 bytes. The last byte is a checksum. Below are lists of ASCII commands, separated in three categories: the list of usual runtime commands, the list of periodic error correction commands, and the list of setup commands.