Scope Photos - Bose Loewe Concertos Acoustimass 61247 Service Manual

Scope Photos

Figure 10. Microcontroller (U202) Scope Photo, Power Up
Upper trace: RESET pulse (active low), U202 pin 14 or U200 pin 2
Middle trace: +5V supply
Lower trace: Serial data from uC, J5 pin 11
The first thing the microcontroller supposed to do when it comes out of reset is to print the
following to the debug output J5 pin 11.
**
%0001#01
This is clearly visible as two bursts of activity (4800 BAUD), one immediately following the rising
edge of the reset line ( ** ) and one approximately 50 msec later (%0001#01).
After printing the boot prompt, the Uc will only print error codes. Thus, a lack of activity on this
signal after the initial two bursts is expected. Short bursts of activity is likely to be the uC printing
out error codes.
Figure 11. Microcontroller 8 MHz clock at U202 pin 39
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