Seca 780 - EEPROM; Serial bus; Fault handling; Time base

In order to avoid measuring errors due to almost flat batteries, their voltage is measured at regular
intervals. If the voltage drops below a certain limit, the user is alerted by the battery symbol in the
LCD. If the next threshold is undershot, „bAtt" is displayed and weighing is no longer possible.
In order to extend the on-time when the scale is mains operated, the microcontroller receives a
signal when a mains transformer is connected.
It is possible to use rechargeable batteries, but the batteries will not be charged in the scale.
EEPROM
The DETF module accommodates an EEPROM on which all parameters are stored that can be used
to influence the program sequence, for example various limit values or the coefficients for
determining the weight and for temperature compensation.
Furthermore, the scale can store values to be retrieved when the scale is switched on the next time,
e.g. the modules last connected.
Serial bus
To allow the scale to be calibrated and additional modules, such as displays, to be connected, the
DETF module is equipped with an interface to the SeSAM bus.
On this bus the stabilized and non-stablized supply voltages are available. Via a data and a clock
pulse line all relevant data is transmitted to other modules. A special start line is provided via which
the scale can be switched on or other modules can signal thatthey wantto send data.
Fault handling
If faults occur, the SeSAM bus initiates a fault message with the relevant fault code. Furthermore,
each fault message includes the number of the module type on which the fault has occurred and a
code which indicates how long the message is to stay on display and which displays are to be
suppressed.
The fault messages are transferred to the SeSAM bus and can be output by the display module
(module type for the DETF module = 1).
The following fault messages are implemented:
10 20 bit counter overflow
11 Counts outside the permissible range
12 Switch-on zeropoint outside the permissible range
13 Zero follow-up outside the permissible range
14 Fault in the kg value calculation
15 Recalibration fault
20 Battery voltage too low
21 Fault in battery voltage measurement
22 Fault in temperature measurement
23
Temperature range exceeded ( < 0°C or > 50°C)
30 General bus fault
32 Command buffer full
33 More than 8 slaves detected
40 EEPROM fault
41 Incorrect EEPROM access
50 Other fault
Instead of fault message 20 „bAtt" is displayed and „temP" instead of fault message 23.
Time base
30-34-00-617 2
06.09.1999
EE/Jensen