Fiat 1996 Brava Service Manual page 438

Engine Bravo-Brava @i i»
Fuel system '98 range
10.
b. Microprocessor
This electronic component calculates and manages the acquired data; in this respect it should be
considered an actual computer mainly responsible for the following: interrogating the memories,
comparing the data being processed with the sample data and managing the actuator control circuits.
c. ROM (Read Only Memory)
This contains all the programs necessary for the operation of the microprocessor; moreover, as it is
permanently programmed before installation in the control unit, its data can be read but not modified.
The ROM is a storage component, so even if the battery terminals are disconnected, the instructions
it contains remain stored in memory.
d. RAM (Random Access Memory)
The RAM is a transition memory in which the data, in addition to being read, can also be stored in
memory.
It is used for both temporary storage of input data in order to render them available for subsequent
processing, and also for the storage of signals for coding operating faults, which can arise on the sen­
sors, actuators or certain functions of the control unit.
The RAM is divided into two sections: the first is volatile and is allocated to data storage; it is enabled
when the ignition is on and cancelled when the ignition is switched off.
The non-volatile section (RAM STAND-BY) is used to store in memory the self-adapting corrections
of the aperture during idling, of the engine idle actuator and the angle position of the fully closed throt­
tle valve. It is also assigned to memorizing the engine parameters and adapting them over time; this
means that the control unit, using mainly the Lambda probe's signal, modifies and stores in memory a
corrective factor of the injection time which influences the mixture strength.
To be maintained, the self-adapting corrections of the idle speed actuator require the continuous
presence of the battery supply (memory in STAND-BY).
If the battery, double relay or control unit connector are disconnected, the parameters are reset. Nor­
mal use of the car will restore the adaptation process and the memorization of the new parameters.
e. EEPROM (Electrical Erasable Programmable Read Only Memory)
This is a particular type of memory which can be deleted electrically and reprogrammed several times.
Its functions include receiving from the STAND-BY RAM records of faults arising during engine op­
eration, and transmitting this information via the diagnostic socket to the diagnostic equipment (EX­
AMINER or SDC station). To delete confirmed faults, use the diagnostic equipment in active diagno­
sis.
The presence of a non-volatile memory also means that data relating to system faults are stored even
if the battery is disconnected, and also indications of faults even after the latter disappear.
f. Drivers (final power stages for driving the actuators)
These are circuits driven directly by the microprocessor and the specific integrated circuit, and they
serve to supply the actuators, namely: fuel injectors, idle control motor, fuel vapour cut-off valve and
fuel pump relay.
26 Publication no. 506.670/74