Sunsea AIoT SimCom SIM7090G User Manual page 31

SIM7090G User Manual V1.01
Figure 11: Reference circuit of level shifter IC
Figure 12: Reference circuit with Transistor
NOTE
When it uses the level shifter IC, the pull up resistance on TXD_3.3V, RTS_3.3V, DCD_3.3V and
RI_3.3V should not be less than 47KΩ.
When it uses the transistor, the selection of the transistor must be a high-speed transistor, and the
model MMBT3904 is recommended.
3.3.2. RI Behavior
The RI pin description:
The RI pin can be used to interrupt output signal to inform the host controller such as application CPU.
Before that, users must use AT command "AT+CFGRI=1" to enable this function.
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