System Troubleshooting and Diagnostics
5.7 Using Loopback Tests to Isolate Failures
5.7.2 Embedded DSSI Loopback Testing
Note
Loopback tests do not test for termination power. Use the following
procedure to check termination power:
Remove the external DSSI cable and terminate Buses 0 and 1. Check
the terminator LEDs to see if termination power is present.
• No termination power at Bus 0 indicates a possible problem with
the internal cable (PN 17–02502–01) that connects DSSI Bus 0
from the backplane.
• No termination power at Bus 1 indicates a possible problem with
the Pico fuse (F3, PN 12–10929–06) on the H3604 console module
or the power harness module (PN 54–19789–01) for the console
module. Refer to Table 5–10 for symptoms of bad fuses.)
Power for DSSI Bus 0 is supplied by the Vterm regulator module,
which plugs into the BA440 backplane. There are no fuses on this
module. Refer to Figure 2–9.
Test 56 tests both SHAC chips (the DSSI adapters). This test can be used
to check both or all four SHAC chips, the internal DSSI (Bus 0) connectivity,
external DSSI cables, and the H3604 DSSI bus interconnect. You must tell
Test 56 what buses to test. You can test either buses 0 and 1 or buses 2 and 3.
Complete the following procedures before running test 56.
1. Make sure the system is powered down, then connect DSSI Bus 0 to DSSI
Bus 1 with a standard external DSSI cable (BC21M–09). Place a DSSI
terminator on the remaining DSSI connector for Bus 1. It is not critical
which Bus 1 connector is used in connecting the cable.
Note
The DSSI bus must be terminated for the tests to execute successfully.
2. Remove all DSSI bus node ID plugs from storage devices on the two buses
to be tested.
3. Install bus node ID plugs on the console module (H3604) so that Bus 0 and
Bus 1 do not have the same bus node ID. For example, assign bus node ID
6 to Bus 0 and bus node ID 7 to Bus 1. Do a SHOW DSSI_ID and verify
that the buses to be tested have unique IDs.
System Troubleshooting and Diagnostics 5–73
