Hanna Instruments mV 600 Series - Manual (Page 22)

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FAULT CONDITIONS AND SELFTEST PROCEDURES
The fault conditions below may be detected by the software:
• EEPROM data error;
• I2C internal bus failure;
• code dead loop.
EEPROM data error can be detected through EEPROM test
procedure at startup or when explicitly requested using setup
menu.
When an EEPROM error is detected, user is given the option
to perform a reset of EEPROM. Thus the reset can be per-
formed whenever needed. It may be useful to provide a means
to reset EEPROM directly (without a previous EEPROM error
detection). This is done by pressing CFM first and then SETUP,
and CAL DATA simultaneously.
Note When an EEPROM reset has been per-
formed calibration data are reset to
default. An intermittent CAL will blink
on the display to advise the user of
this status.
A I2C failure is detected when the I2C transmission is not
acknowledged or a bus fault occurs for more than a certain
number of attempts (this can be due, for example, to dam-
age sustained by one of the ICs connected to I2C bus).
If so, the controller stops any tasks and displays a perpetual
sliding message “Serial bus error” (i.e. this is a fatal error).
STARTUP
At startup the firmware release code scrolls through the LCD;
it is possible to escape from code scrolling pressing any key.
During the automatic startup the Real Time Clock (RTC) is
checked to see if a reset occurred since last software ini-
tialization. In this case, the RTC is initialized with the default
date and time 01/01/1997 - 00:00. An EEPROM reset
does not affect the RTC settings.
The EEPROM is also checked to see if it is new. If this is the
case, the default values are copied from ROM and then
the device enters normal mode. Otherwise an EEPROM
checksum test is performed (the same is performed during
EEPROM selftest procedure).
If checksum is correct, normal mode is entered, otherwise
user is asked whether the EEPROM should be reset.
If EEPROM reset is requested, default values from ROM
are stored into EEPROM as would happen with a new
EEPROM.
Note that EEPROM data is composed of setup data and
calibration data. As for the setup data, the calibration data is
assigned default values when an EEPROM reset occurs. An
un-calibrated meter can perform mea-
surement, though user is informed that
pH calibration (pH models) or mV cali-
bration (mV models) is needed by
means a blinking “CAL” icon.
When the last calibration data is re-
quired, the “no CAL” message is
displayed if no calibration procedure
was performed.
Unlike pH and mV calibration, user has no information on
calibration need for other magnitudes, other than the aware-
ness that EEPROM was reset.
After an EEPROM reset, all calibrations (input and output)
have to be performed in order to obtain correct measure-
ments.