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LG GSA-4040B Service Manual page 86

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HW Self- Diagnostic function
1. Self-Diagnostic Function by LED Blink.
• Basic operation: 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: DSP, S-RAM (1Mb), and Flash-ROM (16Mb) are connected to the exterior Bus of MPU. Even if the
MPU-Bus terminal of DSP short-circuits, it is sufficient and the Bus terminal of S-RAM 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, like S-RAM, the own poor device of DSP, and the open state of IC-
pin, when [poor] not influencing Bas of MPU, it can detect correctly and becomes blink of LED according to
those defects.
• DSP: DSP has MPU-IF, SD-RAM-IF, 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, MPU-IF, SD-RAM-IF, 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
• SD-RAM: SD-RAM is not connected with direct MPU-Bus. SD-RAM is connected with DSP. Therefore,
when the SD-RAM itself is poor, and abnormalities are in Bus and the control signal between DSP and SD-
RAM, SD-RAM is detected as NG.
• EEP-ROM: If EEP-ROM diagnosis reads address 7FF, will be 5A Written in and will read it, if 5A is written, it
is not OK, and it is not written, and 5A can be read, it OKs, and if it cannot read, it will be judged to be NG
(LED blink). Although Correspondence FW is after L038, in the state mounted since the early stages FW of
Flash-ROM were L02B, it cannot perform poor detection of EEP-ROM. Poor detection of EEP-ROM is
attained by D/L [FW].
• 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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