bit| 7901        7902       7903       7904
---+------------------------------------------
 0 | BUSY                   BATT
 1 | CAPS                     E
 2 | ht?[Jap]?              M
 3 | /|\ [Jap]   TEXT       CONST
 4 | 2ndF        CASL       RAD
 5 |             PRO          G        STAT
 6 |             RUN        DE         PRINT
 7 |


BUSY  symbol lights on if the CPU is busy
CAPS  symbol lights on if the CAPS-key is active
2ndF  symbol lights on if it was just pressed (stays until the next key press)
BATT  symbol lights on if voltage drops below 4.1 V
TEXT  symbol lights on if you are in the TEXT editor
PRO   symbol lights on if you are in the BASIC Programming mode
RUN   symbol lights on if you are running a BASIC program
CASL  symbol lights on
STAT  symbol lights on if you are in the statistic mode
PRINT symbol lights on if 11-pin interface is opened for printing
  E   symbol lights on if you caused an arithmetic error in the calculator mode
DEG   symbol lights on if you have selected the degree mode for the trigonometry
RAD   symbol lights on if you have selected the radion mode for the trigonometry
  G   symbol lights on if you have selected the gon mode for the trigonometry
M     symbol lights on if a value not equal 0 ist stored in the calculator mode
CONST symbol lights on if a constant is defined for calculations in run mode