Theory of operation
2-52
10070389 Rev. A
Puritan Bennett™ 700 Series Ventilator System Service Manual
The UI section includes these circuits, which perform the indicated functions:
• The
CPU section
includes a Motorola 68HC16 microcontroller, which operates at 16 MHz.
(The microcontroller chip contains a microprocessor, clock, internal watchdog, memory, an
I/O interface, and A/D converter.) Two EPROMs (Figure 2-39) totaling up to 512 KB contain
the language-specific software for the UI section. These plug into the PCB and must be
retained with the ventilator when a replacement controller PCB is installed. 64 KB of RAM
is used for ongoing calculations and data storage.
• 2 KB of
NVRAM
(nonvolatile RAM) stores critical calculated information including the
serial number, hours of operation, offsets and gains for the transducers (which are based
on the initial data in the EEPROM on the pressure solenoid PCB, and are updated at every
calibration; use the
Update prsol nvram
function in the service menu when replacing the
pressure solenoid PCB), and other service data, and ventilator settings (see Table 2-2). The
NVRAM device plugs into a socket on the PCB. This device must be retained with the
ventilator when a replacement controller PCB is installed.
•
I/O registers
allow control of LEDs in the UI. They also control the battery charger (on the
BBU PCB). They allow monitoring of status throughout the ventilator.
• The
real-time clock
tracks the day and date.
• The
keyboard controller
provides an interface for the keyboard.
• The RS-232
serial communications port
permits connection to an external computer for
uploading/downloading service information and for future communications options. Not
functional if the Communications option is installed (port A on the Communications panel
is used instead).
• The
knob decoder
, used in conjunction with the knob encoder, decodes the direction and
amount of knob movement.
Figure 2-38. Controller PCB
UI section
BD section
BD microcontroller
EPROMS
U70
U79
U80
NVRAM (U6)
UI microcontroller
U69
7-00143
Serial communications port
Motor controller
chipset
Summary of Contents for Puritan Bennett 700 Series
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