Datascope Passport 2, Руководство по обслуживанию

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Passport 2®/Passport 2 LT™ Service Manual 0070-10-0441 2 - 9
Theory of Operation CPU Control Module
2.1.21 SYNC Connector, J22
This connector provides the interface to an external device. There is a provision for an
analog input signal that is fed to the 10 bit A/D converter that is contained with the
Communication processor (916X1). In addition there is a re-created analog output
(ECG_OUT) of the ECG waveform and blood pressure (IBP_OUT).
2.1.22 Docking Connector, J9
The docking interface connector provides the interface between the CPU Control module and
the Base Station or a Comm-Port. The main purpose of the Base Station or Comm-Port is to
provide interface connectors and some interface circuitry that is not part of the CPU Control
module. It is not feasible or practical to include all the connectors on the CPU Control module
itself. The signal groups that are part of the docking interface are shown in the table below:
2.1.23 3.3 Volt Power
The 3.3 Vdc is generated by Synchronous Step-Down Power Supply Controller U47
(MAX767) and associated discrete components. The input to the power supply controller is
+5 Vdc and its output is +3.3 Vdc +/-5% at 750ma. The controller operates a frequency of
300 Khz. The current sense resistor (R32) is connected to the controller using a Kelvin
connection (no current flow in sense lines). The current limit is controlled by current sense
resistor R32.
2.1.24 -12 Volts DC
There is a limited requirement for -12 Vdc @ 30 ma max. The supply voltage was created by
using power inverter U51 (LTC1144) operating at 10KHz. This device takes the +12V1 as
an input and generates -12 Vdc +/- 10% as an output. The -12 Vdc is used by RS-232
buffers U49 and U50 as well as Op-Amp U101.
2.1.25 Communications Processor and Support
The Communications Processor is U22, a Motorola MCF5282 microcontroller operating in
master mode. The board pulls CPRCON* low, which causes the processor to enter this mode
as it comes out of reset. The internal 64.0 MHz clock is generated by the internal synthesizer
from a 8.000 MHz reference crystal, Y600. The crystal operates with roughly sinusoidal
waveforms, and therefore generates less EMI than a square-wave oscillator module. To
further minimize EMI and avoid the need for external pull up resistors, all unneeded dynamic
I/O pins are set as outputs and disabled. This is performed at initial software boot up. This
also helps reduce power dissipation.
The purpose of the Communications Processor is to communicate with Passport 2
measurement modules such as NIBP, Front End, etc. The communications is handled over a
RS-485 module bus, where the Communications Processor is the master and everyone else is
a slave. This processor also handles scanning the front panel keypad, rotary knob, and
updating its LEDs.