Specifications

LEON-G100/G200 - System Integration Manual
GSM.G1-HW-09002-C Preliminary System description
Page 47 of 75
because the module needs RTS active (low electrical level) and CTS is active (low electrical level) when the
module is in active mode and the UART interface is enabled. In the application circuit a loop from the module
DSR output line to the module DTR input line is provided because the module needs DTR active (low electrical
level) and DSR is active (low electrical level) once the module is switched on and the UART interface is enabled.
The DCD and RI lines of the module can be left unconnected and floating. Also in this configuration the UART
interface can be used as AT commands interface, for GPRS data and CSD data communication and for software
upgrades, but without the HW flow control, data delivered by the DTE can be lost.
Figure 32: UART interface application circuit with partial V.24 link (2-wire) in the DTE/DCE serial communication
To avoid an increase in module power consumption, any external signal connected to the UART must be
set low or tri-stated when the module is in power-down mode. If the external signals in the application circuit
connected to the UART cannot be set low or tri-stated, a multi channel digital switch (e.g. Texas Instruments
SN74CB3Q16244) or a single channel analog switch (e.g.Texas Instruments TS5A3159 or Texas Instruments
TS5A63157) must be inserted between the two-circuit connections and set to high impedance when the module
is in power-down mode.
1.11.1.4 MUX Protocol (3GPP 27.010)
The module has a software layer with MUX functionality complaint with [9].
It is a data link protocol (layer 2 of OSI model) which uses HDLC-like framing and operates between the module
(DCE) and the application processor (DTE). The protocol allows simultaneous sessions over the physical link, the
UART. Each session consists of a stream of bytes transferring various kinds of data like SMS, CBS, GPRS, AT
commands in general. This permits, for example, SMS to be transferred to the DTE when a data connection is in
progress.
The following virtual channels are defined:
Channel 0: MUX control
Channel 1: reserve for GPS data
Channel 2-5: free usage
1.11.2 DDC (I
2
C) interface
1.11.2.1 Overview
An I
2
C compatible Display Data Channel (DDC) interface is available with LEON-G100/G200 modules for serial
communication. This interface is exclusively to access u-blox GPS receivers.
LEON-G100/G200
(DCE)
Application Processor
(DTE)
15
16
TxD
RxD
13
14
RTS
CTS
11
10
9
12
DTR
DSR
RI
DCD
TxD
RxD
RTS
CTS
DTR
DSR
RI
DCD
LEON-G100/G200
(DCE)
Application Processor
(DTE)
15
16
TxD
RxD
13
14
RTS
CTS
11
10
9
12
DTR
DSR
RI
DCD
TxD
RxD
RTS
CTS
DTR
DSR
RI
DCD