Chapter 3
3-12
Esprit® Ventilator Service Manual © Respironics, Inc.
REF 580-1000-02 G
Theory of Operation
Main PCB
The CPU and other ventilator logic interact through the system data, address,
and control buses on the main PCB. The main PCB receives input signals from
various keys on the console or touch screen display and sends them to the
CPU. The main PCB also contains signal inputs for non-maskable interrupt,
running on AC, and running on external battery.
The main PCB receives control signals from the CPU and outputs them to
various pneumatic components and console indicators. The main PCB receives
signals from the digital PCB to turn on the indicators for alarm silence, 100%
oxygen, AC power, external battery power, and backup battery status. The main
PCB receives signal from the CPU PCB to turn on the backup alarm, enable
24V, and the
Screen Lock
,
Battery/Charging
, and
Vent Inop
indicators. The
CPU PCB reads the
Accept
key from the main PCB.
The main PCB includes a normal open and normal closed relay that can trigger
the remote nurse call alarm. Interface connectors on the main PCB include the
RS-232, parallel printer, analog output, and remote alarm connectors.
Other signals routed by the main PCB are the reset, MMI PCB reset, sensor
PCB reset, primary alarm, primary alarm failure detection logic, backup alarm,
remote alarm, printer, POST timer, clocked serial interface (CSI) signals, and
the battery 3.6 V.
CPU PCB
The CPU PCB contains the microprocessor, memory, I/O ports, and associated
control circuitry that controls the ventilator. Functional circuits contained on
the CPU PCB include:
•
V851 microprocessor with a 25-Mhz clock.
•
Static RAM that stores ventilator data.
•
EEPROM that stores patient settings.
•
Flash memory that contains ventilator operating software.
•
One time programmable (OTP) memory that stores the POST routine.
•
Internal RS-232 port that receives ventilator data from the touch
screen.
•
Non-maskable interrupt that tells the CPU a power source has been
lost or interrupted.
•
5-msec bus timer that monitors hardware operation.
•
169-msec watchdog timer that monitors software operation.
•
Data address and control bus to the main PCB.
•
Current version includes 2 MB memory capacity (previous versions
included 1 and 1.5, MB).
