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circuit. The dual transient suppression diode protects the serial port and prevents
the damage towards the system from abnormal power level input such as ESD.
Serial port signals are divided into 5 groups:
1)
Data receiving signal RS_RD (Input); Data sending signal RS_TD
(Output).
2)
Traffic signal clearing/sending RS_CTS(Input); Request sending
RS_RTS (Output)
3)
Modem status signal (modem refers to FWT); Carrier wave detection
UART1_DCD (Output); Data terminal ready UART1_DRT (Output)
4)
Serial port indicating UART1_IND (Output). The power level (high/low)
is determined by the serial port line. The power level differentiates
debugging data line and high-speed data line. Low power level indicates
high-speed (230400BPS) and high power level indicates low speed
(115200BPS).
5)
External serial port drive power supply VDD1_RS. The power switch is
controlled by the MSM_P voltage.
The circuits are shown by the following diagrams:
Input power level conversion circuit:
Figure1-4 Input power level conversion circuit
Output power level conversion circuit:
7
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