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S42 Hardware User Guide
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Page 52 of 62
7
Application Diagram
The following schematic shows a typical application of S42. The module is
connected to some MCU running the application layer. MCU and S42use the same
3,3V power supply. The serial interface has RTS/CTS flow control and UICP support in this
example. The optional hangup feature to close down the link is provided. As an option to save
power an external slow clock crystal may be used. The 32,768kHz crystal can be placed on
customers HW or may be optionally on module. Contact Telit sales. All other module pins
may be left unconnected.
Host MCU
VDD
GND
+3V3
GPIO (o)
In this example S is connected to an MCU supporting UICP, RTS/CTS flow control and Hangup.
The slow clock oscillator (32,768kHz ) is optional; it helps to save power during power down states.
470R
S42/AI
E-6,F-6
VSUP
B-1 EXT-RES#
UART-RXD
UART-TXD
UART-CTS#
UART-RTS#
GPIO[4]/Hangup
TXD (o)
RXD (i)
RTS# (o)
CTS# (i)
GPIO (o)
XL-IN/SLCK
32,768kHz CRYSTAL
The crystal is optional. Leave A-6 open
if the crystal is not present.
B-4
D-4
A-6
all GND pads (14) must be connected.
Blocking capacitors not shown.
pushpull or OD
pushpull
A-5 XL-OUT
D-2
F-4
F-3
D-7
IUR-IN#
D-5
IUR-OUT#
GPIO/DTR# (o)
GPIO/DSR# (i)
Figure 20: Typical Application Schematics