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SARA-R4/N4 series - System Integration Manual

UBX-16029218 - R11 System description Page 40 of 157

The configuration and the behavior of the UART signals after the boot sequence are described below:

 The module data output line (RXD) is set by default to the OFF state (high level) at UART initialization.

The module holds RXD in the OFF state until the module transmits some data.

 The module data input line (TXD) is assumed to be controlled by the external host once UART is

initialized and if UART is used in the application. The TXD data input line has an internal active pull-

down enabled on the “00” and SARA-R410M-02B product versions, and an internal active pull-up

enabled on the other product version.

1.9.1.3 UART multiplexer protocol

SARA-R4/N4 series modules include multiplexer functionality as per 3GPP TS 27.010 [8], on the UART

physical link. This is a data link protocol which uses HDLC-like framing and operates between the module

(DCE) and the application processor (DTE) and allows a number of simultaneous sessions over the used

physical link (UART).

The following virtual channels are defined:

 Channel 0:

for Multiplexer control

 Channel 1:

for all AT commands, and non-Dial Up Network (non-DUN) data connections. UDP, TCP

data socket / data call connections via relevant AT commands.

 Channel 2:

for Dial Up Network (DUN) data connection. It requires the host to have and use its own

TCP/IP stack. The DUN can be initiated on modem side or terminal/host side.

 Channel 3:

for u-blox GNSS data tunneling (not supported by “00” and “01” product versions).

1.9.2 USB interface

1.9.2.1 USB features

SARA-R4/N4 series modules include a High-Speed USB 2.0 compliant interface with 480 Mb/s maximum

data rate, representing the main interface for transferring high speed data with a host application

processor, supporting:

 AT command mode

 Data mode and Online command mode

 FW upgrades by means of the FOAT feature (see 1.13.7)

 FW upgrades by means of the u-blox EasyFlash dedicated tool

 Trace log capture (diagnostic purposes)

For the definition of the interface data mode, command mode and online command mode see SARA-R4/N4 series AT Commands Manual [2]

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