Mallinckrodt NELLCOR NPB-4000, Service Manual

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Section 14: Main Color Board Digital Theory of Operation
14-26
The control words sent to the A/D converter contain the A/D multiplexer
channel to convert, the data length, data format, and whether the conversion is a
unipolar or bipolar conversion.
The first bit transferred out the SSIO transmit line is the most significant bit, bit
15. The A/D takes bits 15-8 and the front end takes bits 7-0. Bit definitions are
as follows.
BIT 16-12: A/D MUX CHANNEL SELECT
BIT 11-10: A/D DATA LENGTH
BIT 9: A/D DATA FORMAT
BIT 8: UNIPOLAR/BIPOLAR
Once the A/D reads these 8 bits, a conversion starts.
BIT 7-5: FRONT END MUX CHANNEL SELECT
BIT 4-3: LEAD SELECT
BIT 2: 0.5 HZ FILTER SELECT
BIT 1: BASELINE RESET
BIT 0: PARITY
Once these 8 bits are strobed into the front end serial shift register, a load pulse
is generated which transfers these bits to the output register in the shift register
and these bits now become effective.
14.17 DIGITAL SCHEMATIC
These schematics include all of the above circuits and some additional circuits
which need explanations. The schematic contains the following chips:
386EXMP microcontroller
42MX09 programmable device with the control
circuits
LCD CONTROLLER 1354F0A LCD display control chip
74HCT244 buffer chips for the signals from the
LCD controller to the display itself
74LVC16245 data bus buffer to interface the 386EX
to the other chips
RTC DS1693 real time clock with 64 bytes of battery
backed ram and on board crystal
74LVC541 mux for the address/data to the RTC
DUART dual uart for the RS232 and recorder
MAX211E RS232 interface chip with 15kv ESD
DISPLAY RAM 1MX16 EDO DRAM for the LCD
display
DRAM 1Mx16 EDO dynamic ram memory
74ACT157 address mux for the DRAM
BOOT FLASH bootable/executable flash memory
TREND FLASH flash memory for storing trend data
OSCILLATOR 40mhz oscillator to generate CLK2
The schematics contains the NIBP circuits, the speaker circuits, the battery
voltage and temperature input circuits, the push button interface circuit, and the
backlight interface connector circuit. The 50 pin connector connects to the
recorder, RS-232 connector, the power supply connector, the DEFIB connector,
and the speaker.