LG GSA-4167B Service Manual page 83

HW Self- Diagnostic function
1. Self-Diagnostic Function by LED Blink.
• Basic operation: At JR6, MPU is included in DSP, MPU accesses each peripheral (inside, exterior) device,
and discover a defect by the ability of a read/write of data to be performed correctly. Since MPU operates by
the program with a built-in Flash-ROM, when abnormalities are in MPU, Flash-ROM, and these Data-Bus &
control signals, this self-diagnostic function cannot be used. In such a case, the case where LED does not
light up at all at the time of a power supply injection is almost the case.
• MPU: In DSP Flash-ROM (16Mb) is connected to the exterior Bus of MPU. Even if the MPU-Bus terminal of
Flash-ROM short-circuits, it becomes impossible for MPU to read the right program data from Flash-ROM,
and stops for this reason, turning on LED at all. On the other hand, the own poor device of DSP, and the
open state of IC-pin, when a defect does not influencing Bas of MPU, it can detect correctly and becomes
blink of LED according to those defects.
• DSP: DSP has ATAPI-IF, LDD-serial-IF, AFE-serial-IF, and an AFE control signal as Digital-IF. As Analog-
IF, it has the slice circuit of RF signal from AFE, PLL, the objects ADC and DAC for SERVO, and ADC for
ADIP detection. Among these, own poor Digital of DSP, and AFE-serial-IF can detect by this self-diagnostic
function.
• AFE: Poor detection of AFE is restricted to detection of a limitation-item. Since the greater part of the
function is analog signal processing, AFE serves as a register in AFE, and a check, which accepts it, serial
IF in the logical digital examination from MPU. In addition, serial-IF for AFE control is performed via DSP.
This is writing in the Write command and setting data, and is automatically transmitted to the predetermined
register of DSP. Conversely, when it leads the register information on AFE, the read command can be
written in the predetermined register of DSP, and the value of an AFE register can be read by reading the
read register of DSP after that. Therefore, serial [between the poor register of AFE, and AFE and DSP],
when there is LED blink with poor AFE — the defect of IF or the defect of the register for AFE of DSP is
considered.
• Refer to the contrast table of the number of times of blink of LED, and a poor part.
• The self-diagnostic function by this LED blink is carried out in the state of a set without a PCB independent
or loading Disc.
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