Integration Manual
TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R04 Advance Information Design-in
Page 98 of 141
Providing the TXD, RXD, RTS and CTS lines only (not using the complete V.24 link)
If the functionality of the DSR, DCD, RI and DTR lines is not required in, or the lines are not available:
Connect the module DTR input line to GND using a 0 series resistor, since the module requires DTR active
Leave DSR, DCD and RI lines of the module unconnected and floating
If RS-232 compatible signal levels are needed, the Maxim 13234E voltage level translator can be used. This chip
translates voltage levels from 1.8 V (module side) to the RS-232 standard.
If a 1.8 V Application Processor is used, the circuit should be implemented as described in Figure 53.
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
0Ω
TP
0Ω
TP
TP
TP
TP
Figure 53: UART interface application circuit with partial V.24 link (5-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 54.
5
V_INT
TxD
Application Processor
(3.0V 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
1V8
B1 A1
GND
U1
B3A3
VCCBVCCA
Unidirectional
Voltage Translator
C1
C2
3V0
DIR3
DIR2 OE
DIR1
VCC
B2 A2
B4A4
DIR4
TP
0Ω
TP
0Ω
TP
0Ω
TP
0Ω
TP
0Ω
TP
TP
TP
TP
Figure 54: UART interface application circuit with partial V.24 link (5-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
SN74AVC4T774 - Texas Instruments
Table 34: Component for UART application circuit with partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)