Mindray Passport 5-Lead, Service Manual

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Passport 5-Lead, 5L, LT, XG Service Manual 0070-00-0420 2 - 47
Theory of Operation Block Diagrams
NIBP Module Interface
The NIBP module interface is also an RS-232 interface, currently running at 2400 baud,
eight data bits and no parity. Only the RxD and TxD data lines are used. This interface is
connected to SCC3. The CPU can independently reset the NIBP module using the NRST
signal (port A bit 7). On power-up or reset, the I/O port is default to input, causing the NRST
signal to be pulled up to reset the NIBP module. There is also a reset acknowledge signal
from the NIBP module that can be read from the recorder status register.
8-bit A/D Converter SCP Interface
The A/D converter is a 12 channel (one is used for internal diagnostic) 8-bit serial A/D
converter. It is connected to the SCP interface on the microcontroller. To initiate a conversion,
the CPU writes the A/D channel address to the upper bits of the SCP transmit buffer. When 8-
bit that is read back at the same time would contain the result of the previous A/D
conversion. The clock invert bit in the SCP control register needs to be set to 0 to obtain the
proper clock polarity.
The definition of the A/D channels are as follows:
Most of the inputs are used for diagnostic purposes. In diagnostic mode, all the power supply
levels will be read and displayed. In run time, some of these voltages would also be checked
for proper operation (espe/-15V). The run-time check should be very robust in that it
should not generate false alarms due to noise or other transients (e.g. ESD episodes). A wide
tolerance with probably some form of averaging would be performed.
The raw DC voltage can be checked for whether unit is running on battery (if the voltage is
greater than a certain threshold). When the unit is running on battery, the raw DC voltage
would indicate the battery voltage. A low battery condition exists when the voltage is below
a certain threshold. The proper levels and cutoffs are yet to be defined.
The DAC voltage input can be used to check the operation of the DAC. The ADC diagnostic
voltage can be used to check the operation of the ADC.
The external analog input signal is currently not used.
CHANNEL # SIGNAL DESCRIPTION NOMINAL TOLERANCE
0 +5V 7FH
1 +15V 9CH
2 -15V 2FH
3 Speaker Voltage
4 Raw DC Voltage
5 +12V 7DH
6 DAC output voltage
7 External analog input
8 Reserved
9 Reserved
10 Reserved
11 ADC diagnostic voltage 7FH 7DH-83H