GE Centiva/5 Plus, Technical Reference Manual

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2 Theory of operation
TRM, Centiva/5 Plus, M1047448/CM-922026, rev. 3.50.a of 11/05 2-11
Exp. valve locking motor system
Nebulizer valves
Watchdog
Fan
Microprocessor B
A and B EEPROM
The expiration valve locking motor system (EB E05) is controlled by micro B in
current limiting and movement direction.
The micro B controls the nebulizer valves (EB M20, EB M21 and EB M22) in gas
selection between O2 and Air and duration of opening.
The watchdog (EB S02) controls both microprocessors A and B and turns off the +
15V WD and +13 V WD supply line, in case of detected malfunction of program or
micros. Thus the system is able to shut down in a fail-safe mode.
To avoid possible O2 concentration increase within the housing, caused by leaks, a
fan (EB S10) is exchanging the gas within the housing. The fan supply is fused by
SI11. The fan’s proper operation is monitored by a rotation monitor (EB S11) that
reports to the micro B.
The micro B handles all controls and sensors, as well as the audible alarm indicator
within the main engine and the serial port communication. The B EPROM is loaded
with the control software. The B EEPROM allows storing a “shadow” data set.
Both micros store data, such as calibration and “learned” values into the according
EEPROM in a “father” and “grandfather” sequence. For safety reasons this
sequence is doubled, which results in total in four data store sequences. That is
why successfully performing five (5) system test is necessary for rewriting of all
storage levels after replacing PC board A or B.