Smiths Medical BCI 3304, Service Manual

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Chapter 2: Oximeter Circuit Description
2-8 3304 Service Manual
SIgnAL DeSCRIPTIOn
ANA-5 The -5 volt power supply is filtered to produce ANA-5. ANA-5
powers the analog circuitry.
BP/UP ADC bipolar or unipolar conversion mode selection signal.
CAP-GND Signal used to short blocking capacitor C19 to ground.
CH1/2 ADC channel one or two selection signal.
CKS CKS is the microprocessor’s high-speed, synchronous serial
output clock signal.
CLKIN Clock signal to ADC.
CRS/FIN Coarse / fine ADC sampling mode selection signal.
D0-D7 D0 through D7 are the microprocessor’s data lines. The data
lines are routed to RAM, PROM and peripheral devices.
DISP-LD DISP-LD is used to select display control chips U1 and U2 on the
display board.
INTGRAT,
RST-INT
Signals used to control integrator U4A.
IR-DRV,
RED-DRV,
/IR-ENBL,
/RED-ENBL
Signals used to control MOSFET bridge Q1 and Q2, which
powers probe LED’s.
KEY-INx..
KEY-OUTx..
Keypad input / output scan control signals.
LED-DRV Signal which defines LED drive current.
ME ME is the microprocessor’s memory enable output. ME is routed
to decoder U16A to enable memory decoding.
ON-STBY Line connected to the O/I key.
PFI, /PFO Power fail input and output signals, used to shut down the
monitor if battery is too low.
PHI Clock signal generated by microprocessor.
POT-LD POT-LD is used to select digital potentiometer chip U6.
PRB-DET PRB-DET is used to inform microprocessor if probe is plugged in.
PRB-FAULT Signal used to inform microprocessor about probe cable
problem.
RXS RXS is the microprocessor’s high-speed, synchronous serial input
receiving data signal.
SIGNAL SIGNAL originates at TP9 and is routed to ADC U8 channel one
input.