Integration Manual
TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R04 Advance Information Design-in
Page 99 of 141
Providing the TXD and RXD lines only (not using the complete V24 link)
If the functionality of the CTS, RTS, DSR, DCD, RI and DTR lines is not required in the application, or the lines
are not available, the circuit with a 1.8 V Application Processor should be implemented as described in Figure 55:
Connect the module RTS input line to GND or to the CTS output line of the module: since the module
requires RTS active (low electrical level) if HW flow-control is enabled (AT&K3, that is the default setting),
the pin can be connected using a 0 series resistor to GND or to the active-module CTS (low electrical level)
when the module is in active-mode, the UART interface is enabled and the HW flow-control is enabled
Connect the module DTR input line to GND using a 0 series resistor, as the module requires DTR active
Leave DSR, DCD and RI lines of the module unconnected and floating
TxD
Application Processor
(1.8V DTE)
RxD
RTS
CTS
DTR
DSR
RI
DCD
GND
TOBY-L2 series
(1.8V DCE)
16
TXD
13
DTR
17
RXD
14
RTS
15
CTS
10
DSR
11
RI
12
DCD
GND
0Ω
TP
0Ω
TP
0Ω
TP
TP
0Ω
TP
TP
TP
TP
Figure 55: UART interface application circuit with partial V.24 link (3-wire) in the DTE/DCE serial communication (1.8V DTE)
If a 3.0 V Application Processor is used, appropriate unidirectional voltage translators must be provided using the
module V_INT output as 1.8 V supply, as described in Figure 56.
5
V_INT
TxD
Application Processor
(3.0V DTE)
RxD
DTR
DSR
RI
DCD
GND
TOBY-L2 series
(1.8V DCE)
16
TXD
13
DTR
17
RXD
10
DSR
11
RI
12
DCD
GND
1V8
B1 A1
GND
U1
VCCBVCCA
Unidirectional
Voltage Translator
C1
C2
3V0
DIR1
DIR2 OE
VCC
B2 A2
RTS
CTS
14
RTS
15
CTS
TP
0Ω
TP
0Ω
TP
0Ω
TP
TP
0Ω
TP
TP
TP
TP
Figure 56: UART interface application circuit with partial V.24 link (3-wire) in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1
Unidirectional Voltage Translator
SN74AVC2T245 - Texas Instruments
Table 35: Component for UART application circuit with partial V.24 link (3-wire) in DTE/DCE serial communication (3.0 V DTE)