Mindray Passport 5-Lead, Service Manual

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Passport 5-Lead, 5L, LT, XG Service Manual 0070-00-0420 2 - 57
Theory of Operation Block Diagrams
2.2.8 CO2 Interface Module
The CO2 Interface Module, or CIM, provides the electrical interface between the Passport
monitor and the Novametrics CO2 Control Modules. Some CO2 Interface Modules support
Mainstream CO2 monitoring only while others support Sidestream and Mainstream CO2
monitoring. The CIM provides both buffered data communications as well as power supplies
for the Capnostat.
FIGURE 2-25
CO
2
Interface Module Block Diagram
Overview
An overall block diagram of the CIM is shown in figure. Bus interface logic, consisting of a
programmable logic device, an octal register, and an octal buffer, connects to the Passport’s
pseudo-ISA bus. This bus is shared with the SpO2 module. Therefore, bus resources have
been allocated to avoid conflicts. This interface logic implements two read-write registers,
one for data and the other for control or status. A microcontroller, type 68HC705, operates
as an intelligent, highly buffered UART. The serial port of the microcontroller provides the
data interface to the Mainstream and Sidestream CO2 control modules. The Mainstream
CO2 requires 5 volt and dual 15 volt power for operation. The Sidestream CO2 requires 5
volt and dual 12 volt power supplies for operation. The 5 volt power is supplied directly from
the pseudo-ISA connector. However, the dual 15 volt and 12 volt requirements exceed the
capabilities of the Passport power converter, due to the presence of large pulsations in load
current. Therefore, the CIM contains an additional DC-DC converter to supply these
requirements from the bulk supply. A filter is used to assist in handling the pulsatile load
component. Due to even more stringent power supply requirements, the Sidestream CO2
control module requires an additional cleaner -12 volt supply (-12V capnostat on the block
diagram).