Intel SR1600UR Service Guide - Page 131

Appendix C: LED Decoder

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Appendix C: LED Decoder During the system boot process, the BIOS executes a number of platform configuration processes, each of which is assigned a specific hex POST code number. As each configuration routine is started, the BIOS displays the POST code to the POST Code Diagnostic LEDs found on the back edge of the server board. To assist in troubleshooting a system hang during the POST process, the Diagnostic LEDs can be used to 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. If the bit is set in the upper and lower nibbles, then the corresponding LED is lit. If the bit is clear, then the corresponding LED is off. The Diagnostic LED #7 is labeled as "MSB", and the Diagnostic LED #0 is labeled as "LSB". In the following example, the BIOS sends a value of ACh to the diagnostic LED decoder. The LEDs are decoded as follows: • "Upper nibble bits = 1010b = Ah; • Lower nibble bits = 1100b = Ch; The two are concatenated as ACh. Table 8. POST Progress Code LED Example LEDs Status Upper Nibble LEDs Lower Nibble LEDs MSB LSB LED #7 LED #6 LED #5 LED #4 LED #3 LED #2 LED #1 LED #0 8h 4h 2h 1h 8h 4h 2h 1h ON OFF ON OFF ON ON OFF OFF 1 0 1 0 1 1 0 0 Result Ah Ch Intel® Server System SR1600UR Service Guide 113

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Intel
®
Server System SR1600UR Service Guide
113
Appendix C:
LED Decoder
During the system boot process, the BIOS executes a number of platform configuration
processes, each of which is assigned a specific hex POST code number. As each
configuration routine is started, the BIOS displays the POST code to the POST Code
Diagnostic LEDs found on the back edge of the server board. To assist in troubleshooting
a system hang during the POST process, the Diagnostic LEDs can be used to 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. If the bit is set in the upper and lower nibbles, then
the corresponding LED is lit. If the bit is clear, then the corresponding LED is off.
The Diagnostic LED #7 is labeled as "MSB", and the Diagnostic LED #0 is labeled as
"LSB".
In the following example, the BIOS sends a value of ACh to the diagnostic LED decoder.
The LEDs are decoded as follows:
•
"Upper nibble bits = 1010b = Ah;
•
Lower nibble bits = 1100b = Ch;
The two are concatenated as ACh.
Table 8. POST Progress Code LED Example
LEDs
Upper Nibble LEDs
Lower Nibble LEDs
MSB
LSB
LED #7
LED #6
LED #5
LED #4
LED #3
LED #2
LED #1
LED #0
8h
4h
2h
1h
8h
4h
2h
1h
Status
ON
OFF
ON
OFF
ON
ON
OFF
OFF
Result
1
0
1
0
1
1
0
0
Ah
Ch