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9.8
Diagnostic LEDs
All port 80 codes are displayed using the Diagnostic LEDs found on the back edge of the
baseboard. The diagnostic LED feature consists of a hardware decoder and four dual color
LEDs. During POST, the LEDs will display all normal POST codes representing the progress of
the BIOS POST. Each code will be represented by a combination of colors from the four LEDs.
The LEDs are capable of displaying three colors: Green, Red, and Amber. The POST codes are
divided into two nibbles, an upper nibble and a lower nibble. Each bit in the upper nibble is
represented by a Red LED and each bit in the lower nibble is represented by a green LED. If
both bits are set in the upper and lower nibbles then both Red and Green LEDs are lit, resulting
in an Amber color. If both bits are clear, then the LED is off.
In the below example, BIOS sends a value of ACh to the Diagnostic LED decoder. The LEDs
are decoded as follows:
Red bits = 1010b = Ah
Green bits = 1100b = Ch
Since the red bits correspond to the upper nibble and the green bits correspond to the lower
nibble, the two are concatenated to be ACh.
LEDs
Red
Ach
1
Result
Amber
MSB
9.8.1
Diagnostic LED POST Progress Codes
Diagnostic LED
Decoder
G=Green, R=Red,
A=Amber
Hi
10h
Off
Off
Off
11h
Off
Off
Off
12h
Off
Off
G
13h
Off
Off
G
14h
Off
G
Off
64
Table 75. POST Progress Code LED Example
Green
Red
1
0
1
Green
Table 76. Boot Block POST Progress Codes
Low
The NMI is disabled. Start Power-on delay. Initialization code checksum
R
verified.
Initialize the DMA controller, perform the keyboard controller BAT test, start
A
memory refresh, and enter 4 GB flat mode.
R
Get start of initialization code and check BIOS header.
A
Memory sizing.
Test base 512K of memory. Return to real mode. Execute any OEM patches
R
and set up the stack.
SE7221BK1-E Technical Product Specification
Green
Red
Green
1
0
Red
Description
Red
Green
0
0
Off
LSB
Revision 1.3
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