Mindray VS-800, Service Manual

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Principles of Operation
2-8
2.2.3.2.2 LED
There are Six groups of 7-segment digit display on the key&displays board. They are used for
displaying the systolic pressure, diastolic pressure, mean pressure/cuff pressure, SpO
2
, PR
and Temp; every group is of 3 digits.
The signal is transmitted from the main board FPGA to the CPLD, and is displayed by the
7-segment digit displays driven by the CPLD scanning.
The AC indicator is driven by the ADV voltage output from the power board.
The working status indicator (ON/STADNDBY indicator) is driven by the 3.3V voltage.
The battery indicator is controlled by the flash control signal, ADV signal and /BC signal
together. When the system is powered by the battery only, the CPLD outputs the flash control
signal and the battery indicator flashes; when the system is power by AC mains, the ADV
voltage drives the battery indicator to ON. The /BC signal is transmitted from the power board
to the cathode of the battery indicator. When there is no battery in the monitor, the resistance
of the /BC becomes high, so the battery indicator will never become ON.
The bichrome LED alarm indicator is driven by the 3.3V voltage and controlled by the flash
control signal output from the CPLD.
For other LED indicators, the anodes are connected to 3.3V voltages and are controlled by the
CPLD I/O port.
The displaying and controling is signal of the indicators above is delivered from the main board
FPGA to the CPLD.
2.2.3.2.3 Keys
There are totally 12 keys.
ON/STANDBY key: In the OFF status, press this key to power on the monitor; in the working
status, press this key for less than 1s to enter the standby status. Press this key for more than
2s to power off the monitor.
The other 11 keys form a 3×4 matrix. The CPLD scans the key matrix, and performs the key
debouncing after detecting any key input signal. If the input signal is valid, the CPLD saves the
current key input code and transmits it to the main board.