NCR Customer Display NCR 5972 - Manual (Page 29)

Chapter 3: Installation 3-5
Diagnostics
The 5972 Customer Display has internal Power Up Diagnostics that
occur soon after power‐up or if a Reset Display command is received
from the host software.
When the hardware is powered down, all registers and memory are
lost. No recovery is possible.
The Power Up Diagnostics include the following tests:
• Micro‐controller test
• External character PROM test (VFD only)
• Pixel Number Display
Micro-controller Test
For serial communications, the CTS line is set in a Marking condition
(negative voltage) at the start of the test. For VFD parallel
communications, the Busy line is set active at the start of the test. The
first test is the Micro‐controller test which checks operation at the
Micro‐controller.
If an error is discovered, testing halts, and the firmware begins
executing a forever do nothing loop. No response is sent to the host. If
the Micro‐controller Test passes, the CTS and Busy line exception
conditions are lifted.
External Memory Test Character (VFD Only)
A separate test is performed on the external character PROM, if it
exists. The PROM status is noted and saved for terminal retrieval later
using the Reset command.
If an error is discovered, all character sets stored in the PROM are
considered invalid, and any command received attempting to switch to
one of these character sets is treated as an invalid command and
ignored.