M20 EVB User Guide
3.5. Serial ports
Figure 9: Serial port 0& Serial port 1
Table 6: Pins of Serial Port 0
Pin Signal I/O Description
0_1 DCD0 O Data carrier detection
0_2 TXD0 O Transmit data
0_3 RXD0 I Receive data
0_4 DTR0 I Data terminal ready
0_5 GND GND
0_7 RTS0 I Request to send
0_8 CTS0 O Clear to send
0_9 RI0 O Ring indicator
Table 7: Pins of Serial Port 1
Pin Signal I/O Description
1_2 TXD1 O Transmit data
1_3 RXD1 I Receive data
1_5 GND GND
Customer can debug software through Serial Port 1, which is not for AT command, GPRS service,
CSD call or FAX call.
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