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Initial Troubleshooting and Overall Block Diagram
Initial Troubleshooting
Step 7: Check for Basic CPU Functionality
The Digital Signal Processor (DSP) performs a self-diagnostic test at power up. If the DSP is not working,
the CPU reports an error.
If the DSP does not seem to be working and the CPU did not report the error, then check the CLK_OUT
si
gnal at TP701. It should be a 16 MHz signal. (Refer to Figure 1-5.)
The eight LEDs of DS201 (see Figure 1-5) indicate the status of the boot and flash ROM for the CPU. The
LEDs form a binary code that can be described as a tow digit hexadecimal code. Table 1-3 shows the test
sequence and the LED pattern (binary representation) of the test that is running. If an error occurs and the
te
st is halted the LED pattern will indicate which self test halted the process. The LED closest to R201 is
the place holder for the Least Significant Bit (LSB) in the pattern.
Table 1-3. Sequence for DSP Self-Diagnostic Tests
Test Description Hexadecimal Code
Binary
Repr
es
entation
MSB LSB
LEDs at start of test FF 1111 1111
Checksum test FE 1111 1110
Bootrom RAM test FD 1111 1101
RAM test FC 1111 1100
I/O bus test FB 1111 1011
Main firmware checksum test FA 1111 1010
CPU test AA 1010 1010
Test done and OK 00 0000 0000
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