M20 Hardware Design
TXD0
RXD0
RTS0
CTS0
DTR0
DCD0
RI0
TXD
RXD
RTS
CTS
DTR
DCD
RING
TXD1
RXD1
/TXD
/RXD
Module (DCE)
CUSTOMER (DTE)
Serial port1
Serial port0
Serial port1
Serial port2
Figure 20
: Connection of serial interfaces
Serial Port 0
z
TXD0: Send data to the RXD signal line of DTE
z
RXD0: Receive data from the TXD signal line of DTE
When hardware flow control is required, RTS0 and CTS0 should also be connected. The module
supports hardware flow control in default. When the module is used as a modem, DCD0 and RI0
should be connected. Furthermore, RI0 could indicate the host controller when an event happens
such as an incoming voice call, a URC data export.
Serial Port 1
z
TXD1: Send data to the /RXD signal line of DTE
z
RXD1: Receive data from the /TXD signal line of DTE
Note: Serial port 1 can also support hardware flow control together with RTS1 and CTS1. This
port is only for software debugging and RTS1 and CTS1 flow control do not support in default
firmware.
The logic levels are described in the following table.
M20_HD_V1.01
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Quectel