Appendix D: Post Code Diagnostic Led Decoder; Figure 23. Diagnostic Led Placement Diagram; Table 44. Post Progress Code Led Example - Intel E42249-003 Product Specification

®
Intel Server Board S5500BC TPS

Appendix D: POST Code Diagnostic LED Decoder

The BIOS executes platform configuration processes during the system boot. Each process is
assigned a specific hex POST code number. As each configuration routine is started, the BIOS
displays the POST code on the POST Code Diagnostic LEDs on the back edge of the server
board. The Diagnostic LEDs identify the last POST process to be executed.
Each POST code is represented by the eight amber Diagnostic LEDs. The POST codes are
divided into two nibbles, an upper nibble and a lower nibble. The upper nibble bits are
represented by Diagnostic LEDs #4, #5, #6, #7. The lower nibble bits are represented by
Diagnostics LEDs #0, #1, #2 and #3. Given the bit is set in the upper and lower nibbles, and
then the corresponding LED is lit. If the bit is clear, corresponding LED is off.
Diagnostic LED #7 is labeled as "MSB", and the Diagnostic LED #0 is labeled as "LSB".
A. ID LED
B. Status LED
C. Diagnostic LED #7 (MSB LED)
D. Diagnostic LED #6
E. Diagnostic LED #5
In the following example, the BIOS sends a value of ACh to the diagnostic LED decoder. The
LEDs are decoded as follows:
MSB
LED #7
8h
ON
Status
1
Upper nibble bits = 1010b = Ah; Lower nibble bits = 1100b = Ch; the two are concatenated as
ACh.
Revision 1.0

Figure 23. Diagnostic LED Placement Diagram

Table 44. POST Progress Code LED Example

Upper Nibble LEDs
LED #6 LED #5
4h 2h
OFF ON
0 1
Ah
Intel order number: E42249-003
Appendix D: POST Code Diagnostic LED Decoder
F. Diagnostic LED #4
G. Diagnostic LED #3
H. Diagnostic LED #2
I. Diagnostic LED #1
J. Diagnostic LED #0 (LSB LED)
LED #4 LED #3
1h 8h
OFF ON
0 1
Lower Nibble LEDs
LED #2 LED #1
4h 2h
ON OFF
1 0
Ch
LSB
LED #0
1h
OFF
0
99