User's Manual

Smart Machine Smart Decision
SIM7600SA-H_User Manual_V1.00 2017-10-11
TXB0108RGYR provided by Texas Instruments is recommended. The following figure shows the
voltage matching reference design.
TXD
RXD
RTS
CTS
DTR
DCD
RI A7
A1
A2
A3
A4
A5
A6
MODULE
TXB0108RGYR
UART port
A8
B7
B1
B2
B3
B4
B5
B6
B8
VCCA
OE
VDD_1V8 or
External 1V8
100nF
3.3V
100nF
VCCB
GND
TXD_3.3V
RXD_3.3V
RTS_3.3V
CTS_3.3V
DTR_3.3V
DCD_3.3V
RI_3.3V
47K 47K
Figure 15: Reference circuit of level shift
To comply with RS-232-C protocol, the RS-232-C level shifter chip should be used to connect
SIM7600SA-H to the RS-232-C interface, for example SP3238ECA, etc.
Note: SIM7600SA-H supports the following baud rates: 300, 600, 1200, 2400, 4800, 9600, 19200,
38400, 57600, 115200, 230400, 460800, 921600, 3200000, 3686400, 4000000bps. The default
band rate is 115200bps.
3.3.2 RI and DTR Behavior
The RI pin can be used to interrupt output signal to inform the host controller such as application
CPU.
Normally RI will keep high level until certain conditions such as receiving SMS, or a URC report
coming, and then it will change to low level. It will stay low until the host controller clears the
interrupted event with “AT+CRIRS” AT command.
Idle
HIGH
LOW
Receiving SMS and any
URC report coming.
AT+CFGRI=1
RI
Clear by AT+CRIRS
Idle
HIGH
LOW
Receiving SMS .
AT+CFGRI=0
RI
Clear by AT+CRIRS
Figure 16: RI behaviour（SMS and URC report）
Normally RI will be kept at a high level until a voice call, then it will output periodic rectangular
wave with 5900ms low level and 100ms high level. It will output this kind of periodic rectangular
wave until the call is answered or hung up.