Ublox SARA-N210, Руководство по системной интеграции

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SARA-N2 series - System Integration Manual
UBX-17005143 - R06 System description Page 18 of 82
The CTS output line can be configured as RING indicator, to signal an incoming message received by
the module or an URC event, or as Network status indicator (for more details see section
1.10 and the
SARA-N2 series AT Commands Manual [3 ], +URING, +UGPIOC AT commands).
☞
Hardware flow control lines CTS and RTS are not supported by "02" product versions.
The UART interface provides RS-232 functionality conforming to the ITU-T V.24 Recommendation
(more details available in ITU Recommendation
[5] ): SARA-N2 series modules are designed to operate
as a cellular modem, which represents the Data Circuit-terminating Equipment (DCE) according to
ITU-T V.24 Recommendation
[5] . The application processor connected to the module through the
UART interface represents the Data Terminal Equipment (DTE).
☞
The signal names of the SARA-N2 series modules’ UART interface conform to the ITU-T V.24
Recommendation
[5] : e.g. the TXD line represents the data transmitted by the DTE (application
processor data line output) and received by the DCE (module data line input).
Figure 7 describes the 8N1 frame format, which is the default configuration with fixed baud rate.
D0 D1 D2 D3 D4 D5 D6 D7
Start of 1-Byte
transfer
Start Bit
(Always 0)
Possible Start of
next transfer
Stop Bit
(Always 1)
t
bit
= 1/(Baudrate)
Normal Transfer, 8N1
Figure 7: Description of UART default frame format (8N1) with fixed baud rate
1.9.1.2 UART signal behavior
At the module switch-on, before the UART interface initialization (as described in the power-on
sequence reported in
Figure 5 ), each pin is first tri-stated and then is set to its related internal reset
state. At the end of the boot sequence, the UART interface is initialized and the UART interface is
enabled as AT commands interface.
The configuration and the behavior of the UART signals after the boot sequence are described below.
See section
1.4 for definition and description of module operating modes referred to in this section.
RXD signal behavior
The module data output line (RXD) is set by default to the OFF state (high level) at UART initialization.
The greeting message is sent on the RXD line after the completion of the boot sequence to indicate
the completion of the UART interface initialization.
The module holds RXD in the OFF state until the module does not transmit some data.
TXD signal behavior
The module data input line (TXD) is assumed to be controlled by the external host once UART is
initialized.
There is no internal pull-up / pull-down inside the module on the TXD input.