33
5
7
8
F
E
D
C
B
A
5
7
8
GM-8437ZT/WL
If anything is wrong with IC301 or IC311 (AK7706VTA), DSP error will result. Under the
occurrence of the error, DSP IC will be required to execute the initialization command by the
system microcomputer until DSP IC gets back to normal. However, the error cannot be fixed
because of defective IC, and so the initialization will be commanded over and over again.
While this condition prevails, follow the description below about observations of the IC101
waveforms to distinguish defective DSP IC.
[Observations of the IC101 waveforms]
• First, perform the 67 pin (
drst
) waveform observations.
When DSP error occurs, this waveform repeats "Hi/Low" shapes after ACC ON.
For reference sake, when there is no problem, the 67 pin (
drst
) waveform should
keep "Hi" continuously after ACC ON.
• Then, perform the 19 pin (DSPCHIP) waveform observations.
While the 67 pin (
drst
) waveform stays at "Low", perform the 19 pin waveform
observations and produce a decision.
• The 19 pin (DSPCHIP) waveform during DSP error
Keeping "Hi" continuously : IC301 is defective.
Proper IC311 operation is not guaranteed, though.
After making repairs on IC301, re-perform the 67
pin (
drst
) waveform observations. Keeping "Hi"
continuously on the 67 pin (
drst
) waveform shows
that DSP IC functions normally.
Keeping "Low" continuously : IC311 is defective. IC301 is OK. After making repairs
on IC311, re-perform the 67 pin (
drst
) waveform
observations. Keeping "Hi" continuously on the 67 pin
(
drst
) waveform shows that DSP IC functions normally.
Hi(5V)
Low(0V)
500ms
IC301 is defective
(No information about IC311)
Hi(5V)
Low(0V)
Hi(5V)
Low(0V)
Hi(5V)
Low(0V)
2
The waveform to indicate that
IC311 is defective
-
The 67 pin (
drst
) waveform
during normal DSP operation
[Observations of the IC101 waveform (for
drst
and DSPCHIP)]
7.1.3 THE METHOD OF DISTINGUISHING DEFECTIVE DSP IC (IC301 OR IC311)
DURING DSP ERROR
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