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DNT900 - 08/16/10
Pad
Name
I/O
Description
27
RSVD
-
Reserved pad. Leave unconnected.
28
RSVD
-
Reserved pad. Leave unconnected.
29
RSVD
-
Reserved pad. Leave unconnected.
30 /HOST_RTS I
UART flow control input. The host sets this line low to allow data to flow from the DNT900 on the
RADIO_TXD pin. When the host sets this line high, the DNT900 will stop sending data.
31 RADIO_TXD O
UART transmitter output. The DNT900 sends serial data to the host on this pin. The sleep mode
state of this pin is configurable.
32
RADIO_RXD
I
UART receiver input. The DNT900 receives serial data from the host on this pin.
33 /HOST_CTS O
UART or SPI flow control output. The DNT900 sets this line low to indicate it is ready to accept data
from the host on the RADIO_RXD or MOSI input. When the DNT900 sets this line high, the host
must stop sending data. The sleep mode state of this pin and /DCD is jointly configurable.
34 VMOD O
Module’s +3.3 V regulated supply output. Connect to pad 3 to support 3.3 V full scale and/or
ratiometric ADC readings, etc. Current drain on this output should be no greater than 5 mA.
35 /SS I/O
SPI active low slave select. This pin is an output when the DNT900 operating as a master, and an
input when it is operating as a slave.
36 MOSI I/O
SPI master out, slave in function. This pin is an output when the DNT900 is operating as a master,
and is an input when the DNT900 is operating as a slave.
37 MISO I/O
SPI master in, slave out function. This pin is an input when the DNT900 is operating as a master,
and is an output when the DNT900 is operating as a slave.
38 SCLK I/O
SPI clock signal. This pin is an output when operating as a master, and an input when operating
as a slave.
39
/RESET
I
Active low module hardware reset.
40
RSVD
-
Reserved pad. Leave unconnected.
Table 3.2.1
3.3 DNT900 Antenna Connector
A U.FL miniature coaxial connector is provided on both DNT900 configurations for connection to the
RFIO port. A short U.FL coaxial cable can be used to connect the RFIO port directly to an antenna. In this
case the antenna should be mounted firmly to avoid stressing the U.FL coaxial cable due to antenna
mounting flexure. Alternately, a U.FL coaxial jumper cable can be used to connect the DNT900 module to
a U.FL connector on the host circuit board. The connection between the host circuit board U.FL connector
and the antenna or antenna connector on the host circuit board should be implemented as a 50 ohm
C o p p e r
G r o u n d
P l a n e
C o p p e r
S t r i p l i n e
T r a c e
F R - 4 P C B
M a t e r i a l
C i r c u i t B o a r d S t r i p l i n e T r a c e D e t a i l
F o r 5 0 o h m i m p e d a n c e W = 1 . 7 5 * H
Figure 3.3.1