Mindray Passport 5-Lead, Service Manual

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Passport 5-Lead, 5L, LT, XG Service Manual 0070-00-0420 2 - 35
Theory of Operation Block Diagrams
2.2.3.1 Masimo/Nellcor SpO2 Interface Board
Overview
The Passport Masimo/Nellcor SPO2 Interface Module, (0670-00-0665-01= Masimo, -02 =
Nellcor) or PM/NIM, provides the electrical interface between the Passport monitor and a
Masimo or Nellcor OEM Pulse Oximetry Module. The PM/NIM provides both buffered data
communications as well as power supplies for the Masimo or Nellcor Module.
FIGURE 2-14 Masimo/Nellcor SpO
2
Interface Module Block Diagram
An overall block diagram of the PM/NIM is shown above. 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 CO2 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 68HC705 microcontroller
operates as an intelligent, buffered UART. The serial port of the microcontroller provides the
data interface to the SpO2 Module. All microcontroller data and control lines interfaced to
the SpO2 Module are opto isolated. Power to the SpO2 Module is isolated by a DC-DC
converter module with its input coming directly from the Line/Battery Supply Module.
The SpO2 Modules communicate serially at 9600 baud. A microcontroller is used as a
“smart” UART. A microcontroller can be programmed to understand either the Masimo
protocol or the Nellcor protocol, and can thus buffer the data in an intelligent manner.