Troubleshooting Terminal, Printer, and Serial Device Connections - Edition 5 (32022-90058)

Troubleshooting Procedures
Testing DTC Device Connections
Chapter 2
29
Testing DTC Device Connections
This section applies if only one device is affected and simple causes have been ruled out.
In this case, it is appropriate to use TermDSM for more detailed diagnostics. This must
be done from another terminal or the console.
TermDSM is part of the Online Diagnostic Subsystem. The diagnostics in this section
require security level 2 (SM, DI, or OP capability). For details on running TermDSM,
refer to Chapter 3, “Introduction to TermDSM,” and Chapter 4, “TermDSM Commands.”
TermDSM provides four tests to exercise the DTC device data path. In addition,
TermDSM provides dump and reset functions for the port serving that device.
A port dump writes data to a disk file from port buffers. The dump file can be analyzed
by an HP representative for detailed diagnosis of software faults. A port reset terminates
the session at that port and resets the software managers controlling it.
NOTE Always dump a port before resetting it or performing diagnostic tests. The dump file
provides a record of the problem which will be helpful if the problem occurs again.
Using TermDSM, you can quickly isolate a fault to within the DTC, the device, or the
device cable. The four DTC-device connection tests are:
• Internal Port Loopback Test. Tests the DTC serial interface card (SIC) circuitry for
the port that serves the affected device. Additional hardware is not required; the
affected device can remain connected.
• External Port Loopback Test (for DTC 16s and DTC 48s only). Checks the same
circuitry, plus the driver, and the DTC connector for that port. The device is
disconnected for this test; a loopback connector is required. Use the loopback
connector provided with the DTC for the test.
• Terminal Write/Read Test. Checks the entire DTC device connection. This includes
the SIC circuitry, the driver, the DTC connector, the device cable, and part of the
device circuitry. TermDSM writes a line of characters to the device, then reads it
back, comparing the two. The affected device remains connected. This test is useful
for only supported terminals and PCs.
• Print-to-Port Test. This test is similar to the Terminal Write/Read Test. However, the
character string is transmitted only (not read back by TermDSM). The user must
check visually that the string received at the affected device is the same as was sent.
The test is available for all devices.
Your choice of test will depend on:
• The type of device you are testing (supported or unsupported; terminal or printer).
• The availability of the appropriate loopback connector.
The tests can be used individually, or they can be used together to systematically isolate
the fault. If used together, the following are recommended test sequences. For details on
these tests, refer to Chapter 3, “Introduction to TermDSM,” and Chapter 4, “TermDSM
Commands.”
The test sequence to use for supported devices is as follows:
1. Internal Port Loopback Test.