Telebit T3000 Reference Manual page 145

When you tum the modem on or enter the &T9
command, the modem performs the following
diagnostic tests:
• ROMTest
• RAM Addressing Test
• RAM Read/Write Test
• EEPROM Test
• Loopback Test
• Signal Processor Test
Successful completion of the first three tests means
that the modem's firmware is intact and that the
memory is operating correctly.
During the EEPROM test, the modem reads a
checksum, which tests the integrity of the nonvolatile
memory. If the checksum is correct, Profile A or B
register settings stored in nonvolatile memory are
loaded into memory. If the checksum is incorrect, the
factory default settings are loaded. Which
configuration the modem loads depends on the
current setting of the S255 register.
The final two tests check the loopback capability of
the digitaVanalog interface chip and verify that the
signal processor chip is operating correctly.
7-2 Troubleshooting