Kontron COMe-cP2020 - Manual (Page 57)

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COMe-P2020 User Guide
57
• POST Mode: LEDs build a binary vector to display POST code during the pre-boot phase. In doing so, the higher 4-bit
nibble of the 8-bit POST code is displayed followed by the lower nibble followed by a pause.
• Mode A: LEDs controlled by CPU
Beside the configurable functions described above the LEDs fulfill also a basic debug function during the power up phase as
long as the first access to POST Code LOW Byte Register (0x080) is processed. If a LED lights red and stays red, then a basic
error is present on the board.
The following debug functions are defined and displayed during this initialization phase:
• LED3: PGOOD failure, Power Good status not reached
• LED2: not used
• LED1: CPU reset is asserted/not asserted
• LED0: U-Boot boot failure
Table 3-37: 0x290: LED Configuration Register
ACTION D7 D6 D5 D4 D3 D2 D1 D0
READ 0 0 0 0 LCON
WRITE NU NU NU NU LCON
POWER UP 0 0 0 0 0000
BITFIELD DESCRIPTION
[D0-D3] LCON Use specif ic LED conf iguration:
"0000" = POST
"0001" = Mode A (General Purpose Mode)
others = Reserved
Table 3-38: 0x291: LED Control Register
ACTION D7 D6 D5 D4 D3 D2 D1 D0
READ 0000 LED3 LED2 LED1 LED0
WRITE NU LED3 LED2 LED1 LED0
POWER UP 0000 0 0 0 0
BITFIELD DESCRIPTION
[D0] LED0 LED Control Register, controls Board LED D5:
'0' = LED is OFF
'1' = LED is ON
[D1] LED1 LED Control Register, controls Board LED D6:
'0' = LED is OFF
'1' = LED is ON
[D2] LED2 LED Control Register, controls Board LED D7:
'0' = LED is OFF
'1' = LED is ON
[D3] LED3 LED Control Register, controls Board LED D3:
'0' = LED is OFF
'1' = LED is ON