Service manual

Troubleshooting 3-25
Example 3–12 shows a diagnostic session. Test masks stored in the NVRAM on the
standard I/O module control power-up diagnostic testing. The SCM reads the test masks
and executes the tests designated by the mask. The first quadword masks the SROM
tests and XSROM tests 10 through 3a, and the second quadword masks the remainder of
the XSROM tests. By default all tests are run during power-up including XSROM test
58 which loads the console into memory and all CPUs jump to that code and start. If the
console is loaded and all CPUs are running console, no diagnostics can be run in SCM
user mode.
The following shows the bits set in the SROM/XSROM masks controlling diagnostic tests
during power-up. All bits in the mask are set including those that correspond to
placeholders.
First quadword mask:
|--------- XSROM tests 10 through 3a ----------------------------|-SROM tests 0 f -|
F F F F F F F F F F F F F F F F
1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111
3333 3333 3333 3333 2222 2222 2222 2222 1111 1111 1111 1111 fedc ba98 7654 3210
fedc ba98 7654 3210 fedc ba98 7654 3210 fedc ba98 7654 3210
Second quadword mask:
|--------XSROM tests 40 through 5f ----------|
0 0 1 F F F F F F (hex)
0000 0000 0001 1111 1111 1111 1111 1111 1111 (bits set)
5555 5555 5555 5555 4444 4444 4444 4444 (hex test number)
fedc ba98 7654 3210 fedc ba98 7654 3210
The show nvram command reads the contents of the NVRAM.
The default SROM mask tells the SRM to run all SROM tests. Note that the
NVRAM is read in bytes and leading zero nibbles are suppressed.
The default XSROM mask tells the SRM to run all the XSROM tests. The bit that
is set above the
controls test 58(h) which unloads the console.
test &pc0 5 tells the SCM to run SROM test 5 on CPU0. Note that the CSB
address c0 is used to designate the target CPU. See Example 3–12.
The test fails because the SRM console code, not the SROM code, is running in the
CPU.
Use the SCM command set xsrom_mask none to instruct the SCM not to execute
any XSROM tests and not unload the console code.
The show nvram shows that no bits are set in the XSROM_MASK.