B
I
PAP S
YNCHRONY
S
ERVICE
& T
ECHNICAL
I
NFORMATION
1032410, R
EV
. 00
T
HEORY
OF
O
PERATION
- P
AGE
2
JTAG interface for boundry scans and a power management controller for sleep and wakeup
operations.
The core and I/O ports of the microcontroller use 3.3 V connected at several pins shown on the
schematic.
There is an eight channel successive approximation Analog to Digital Converter (ADC) on this
microcontroller. Channels AD0 through AD7 are all in use.
When power is initially supplied to the chip, the main oscillator is off until the PLL is enabled. Until this
is done, the chip is clocked off of the 32.768 kHz crystal, Y2. The main oscillator takes the output from
fundamental crystal, Y1 and is capable of multiplying this frequency up to 33 MHz.
The computer uses the watch crystal (Y2) and a lithium battery (B1) to maintain an internal clock that
consumes very little power. The lithium coin cell battery (B1) provides a minimum of 17 years of
battery life for the Main PCA.
The main board uses both channels of the two channel 10 bit DAC to control motor speed and set the
output pressure controlled by the valve sleeve. The range of the output voltage is 0 to 3.3V. The
motor speed command is a calibrated non-linear relationship between RPM and DAC counts.
This device features a Serial Peripheral Interface (SPI) that communicates with external devices in
either master or slave mode. Two external devices on the board use this type of communication, the
EEPROM (U1) and the ADC (U11). The microcontroller provides three universal sychronous/
asynchronous receiver/transmitters. The zero transmitter, TXD0, is used for communication with the
humidifier. TXD1 and RXD1 are used for two way communications with a PC via the SleepLink card or
to communicate with an external smart modem.
IR C
OMMUNICATION
L
INK
FOR
THE
I
NTEGRATED
H
UMIDIFIER
The BiPAP Synchrony communicates serially via an infrared LED with the integrated humidifier that
cradles the enclosure. The LED (CR3) transmits 2 wire serial commands to an IR detector inside the
humidifier to turn on, turn off and adjust the water temperature in the humidifier.
8
KBIT
EEPROM
Eight thousand bits of memory are provided on this board for the storage of therapy parameters in U1.
4M
BITS
OF
P
ROGRAM
F
LASH
M
EMORY
IC, U4 contains 512 kbytes of non-volatile Flash memory that is programmed and operated with 3.3V.
This chip contains the application software.
128
KBYTES
OF
A
SYNCHRONOUS
SRAM
U5 has 128 kbytes of static ram which allows for the freedom and complexity of the application code.
This chip is designed for 3V operation.
W
ATCHDOG
S
UPERVISOR
An external supervisory chip, U3, monitors the 3.3 Volts. When the voltage approaches 2.93 V the
chip will protect the Flash Chip by resetting the processor before the voltage reaches a level too low for
the Flash and also shuts down the processor while the core voltage is dropping.
