User's Manual

Smart Machine Smart Decision
SIM7100A_User Manual_V1.01 2014-12-11
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The SIM7100A UART is 1.8V interface. A level shifter should be used if user’s application is equipped
with a 3.3V UART interface. The level shifter TXB0108RGYR provided by Texas Instruments is
recommended. The reference design of the TXB0108RGYR is in the following figures.
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 17: Reference circuit of level shift
To comply with RS-232-C protocol, the RS-232-C level shifter chip should be used to connect SIM7100A
to the RS-232-C interface. In this connection, the TTL level and RS-232-C level are converted mutually.
SIMCom recommends that user uses the SP3238ECA chip with a full modem. For more information
please refers to the RS-232-C chip datasheet.
Note: SIM7100A supports the baud rate: 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600,
115200, 230400, 460800, 921600, 3200000, 3686400, 4000000bps. Default rate is 115200bps.
3.4 USB Interface
SIM7100A module contains a USB interface. This interface is compliant with the USB2.0 specification as
a peripheral or embedded host. USB charging is not supported.
Table 14: USB Pin description
Pin name Pin No. Description
USB_VBUS 11
Valid USB detection input ，Valid USB detection voltage is
3.0-5.25V.
USB_DP 13
USB 2.0 specification-compliant as a peripheral or embedded
host
USB_DN 12
USB_ID 16
High-speed USB ID input. If keep USB_ID pin open, SIM7100A
will be a USB device. If tie USB_ID pin to ground, SIM7100A
will be a USB host controller.