Detailed descriptions   
16.4 I/O Address Areas 
  SIMATIC IPC427C 
140  Operating Instructions, 04/2009, A5E02414743-01 
16.4.5  Output register LED 1 / 2 (read/write, address 404Eh) 
Meaning of the bits 
 
Output register LED 1 / 2 (read/write address 404Eh) 
Bits   
15  14  13 - 8  7  6  5 - 0   
  1      1    LED L1 / SF dark (default) 
  1      0    LED L1 / SF lights yellow 
  0      1    LED L1 / SF lights red (= group fault) 
1      1      LED L2 / R/S dark (default) 
1      0      LED L2 / R/S lights yellow (= STOP) 
0      1      LED L2 / R/S lights green (= RUN) 
    xxxxxx      xxxxxx  Reserved (read/write) 
 
 
 
Note 
The L1 and L2 LEDs indicate by flashing alternatively yellow the progress of the BIOS self-
test during the device startup. When the BIOS self-test is completed, the L1 and L2 LEDs go 
dark.