External Functions; Startup - Hanna Instruments HI 710 Series Instruction Manual

WATCHDOG
When a dead loop condition is detected a reset is automati-
cally invoked.
The effectiveness of watchdog capability can be tested through
one of the special setup items. This test consists of executing
a dummy dead loop that causes watchdog reset signal to be
generated.

EXTERNAL FUNCTIONS

HOLD FUNCTION
This function allows to perform the maintenance
procedures. When the relevant digital insulated
input (terminals #6 on page 7) is on, the ana-
log output is frozen at its last value and control
and alarm relays are disabled. The "Hld" indi-
cation is displayed on the secondary LCD when
the function is active. A 5 to 24 VDC voltage
can be applied to this input.
While in hold state, it is possible to display the
temperature reading on the secondary LCD
pressing the right arrow key. Only when the key
is released, the secondary LCD returns auto-
matically after a few seconds to the "Hld"
indication.
PRESETTABLE TIMER (CLEANING FUNCTION)
A timer is presettable by software to close a digi-
tal insulated contact (terminals #5 on page 7)
after a user programmable time interval with a
minimum interval of 1 day (e.g. for probe clean-
ing function). The time interval is programmable
in number of days through setup code 72.
This output is ON for the period set through setup code 77
(this period can be also changed when the output is ON).
The starting time of the cleaning timer can be set through
setup codes 73, 74, 75 and 76.
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STARTUP

During the automatic startup the Real Time Clock (RTC) is
checked to see if a reset occurred since last software initial-
ization. In this case, the RTC is initialized with the default
date and time 01/01/1998 - 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 check-
sum test is performed (the same is performed during EEPROM
selftest procedure).
If checksum is correct, normal mode is entered, otherwise the
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 measurement, though user
is informed that EC or TDS calibration is needed by means of
a blinking "CAL".
When the last calibration data is re-
quired, the "no CAL" message is
displayed if no calibration procedure
was performed.
Unlike EC/TDS calibration, the user has no information on
calibration need for other ranges, other than the awareness
that EEPROM was reset.
After an EEPROM reset, all calibrations (input and output)
have to be performed in order to obtain correct measure-
ments.
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