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Service Manual Technical overview 127
Mainstream Board
The MSP Board is divided into isolated and non-isolated circuitry.
Non-Isolated Circuitry. The Non-Isolated circuitry on the MSP Board interfaces with the
monitor, the printer, the speaker, P6 and P7 expansion connectors, and with the
Mainstream Processor which resides on the isolated section of the MSP Board.
Isolated Circuitry. The Isolated Circuitry directly controls the hardware responsible for
the CO
2
measurement function.
CPU Circuitry. The CPU Circuitry includes the Philips 80C552 micro controller, 32K of
RAM, 64K of ROM, and standard RESET circuitry.
A UART directly interfaces with the pulse oximetry SpO
2
Board providing the SpO
2
measurement function.
The CO
2
and SpO
2
functions are isolated from all other subsystems in the monitor or
Expansion Modules, but not from each other.
co2 block
PRINTER
I/F CONN.
EXP.
#1 CONN.
EXP.
#2 CONN.
SPEAKER
I/F CIRC.
NON-ISO
POWER
IPC EXP.
CIRC.
ISO PWR
TRANS.
OPTO
COUPL.
OPTO
COUPL.
ISO PWR
SUPPLY
SPO2
I/F CIRC.
SPO2
XDUCER
AND
CONN.
MSP NON-ISOLATED CIRCUITRY
SSP NON-ISOLATED CIRCUITRY
MSP ISOLATED CIRCUITRY
CAPNOGRAPHY FUNCTIONAL BLOCK DIAGRAM
1097-13
PUMP
CONTROL
SIDE-
STREAM
STICK
PCB
CPU
A/D
CONV.
&
MULTIPLEX
CONTROL
INFRARED
SOURCE
DETECTOR
CONTROL
MOTOR
DRIVE
MOTOR
SENSE
(POSITION)
PRESSURE
SENSORS &
AMPLIFIERS
WATER
TRAP
DETECTOR
PUMP
FILTER
PUMP
(Pneumatic connections
not shown.)
NELLCOR
SPO2
BOARD
CPU
A-D
CONV.
INFRARED
SOURCE
DET.
BIAS
CIRC.
HEATER
CIRC.
MOTOR
DRIVE
POSN.
SENSE
DET.
SIGNAL
DET.
TEMP.
BARO.
CO2
SENSOR
AND
CONN.
EXTENDER
BOARD
CO2 SIGNAL
TEMPERATURE