$90/144:   Kernal I/O Status Word ST

   +-------+---------------------------------+
   | Bit 7 |   1 = Device not present (S)    |
   |       |   1 = End of Tape (T)           |
   | Bit 6 |   1 = End of File (S+T)         |
   | Bit 5 |   1 = Checksum error (T)        |
   | Bit 4 |   1 = Different error (T)       |
   | Bit 3 |   1 = Too many bytes (T)        |
   | Bit 2 |   1 = Too few bytes (T)         |
   | Bit 1 |   1 = Timeout Read (S)          |
   | Bit 0 |   1 = Timeout Write (S)         |
   +-------+---------------------------------+

   (S) = Serial bus, (T) = Tape

Kernal-Reference:

 AND $90     : $F4F5
 BIT $90     : $EE79 $F249 $F28A $F524
 LDA $90     : $F1AD $F3ED $F4DA $F505 $F55D $FE1A
 ORA $90     : $FE1C
 STA $90     : $F311 $F3DF $F4A9 $F4F7 $F843 $FE1E

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