Mindray VS-800, Service Manual

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Principles of Operation
2-5
2.2.1.3 Units of main board
2.2.1.3.1 FPGA
FPGA is used for:
Controlling STN-LCD
The PFGA drives the display of the monochromatic STN-LCD module, including the RAM and
displaying sequence; it communicates with the key&displays board CPLD.
The FPGA transmits data displayed by LEDs and receives key information by Means of
communicating with keypad CPLD through synchronous serial port.
Extending serial ports
The FPGA extends 3 serial ports for the communications with parameter modules.
Extending I/O port
The FPGA extends the I/O port for controlling the NURSE CALL circuit.
Generating frequency-adjustable signal
The FPGA generates the frequency-adjustable signal which is used by the audio process
circuit.
2.2.1.3.2 Audio process circuit
Following the common scheme regarding the key&displays board audio process circuit, the
audio process circuit generates envelope signals by using the PWM function of the CPU, and
generates audio frequency signals by using the FPGA.
2.2.1.3.3 ADC circuit
The ADC circuit detects ADV, +12V and battery voltages as well as the battery status voltage
by using the A/D converter. The A/D converter Provides a I
2
C bus interface. The CPU
simulates the I
2
C bus signal with two I/O ports.
2.2.1.3.4 Network connector
To guarantee that the earth wire of the network connector can pass the 1500V high-voltage
test, isolated components such as the network transformer must be placed near the RJ45
socket and kept a specific distance from other components.
2.2.1.3.5 RS232 connector
The RS232 connector is made of the UART module of the CPU and the RS232 chip. The
RS232 chip has the ESD protection function (±15KV).