TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R07
Advance Information
Design-in
Page 108 of 158
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 58.
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
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
TP
TP
TP
Figure 58: 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 (DTE) is used, then it is recommended to connect the 1.8 V UART interface of the
module (DCE) by means of appropriate unidirectional voltage translators using the module
V_INT
output as
1.8 V supply for the voltage translators on the module side, as described in Figure 59.
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
B3
A3
VCCB
VCCA
Unidirectional
Voltage Translator
C1
C2
3V0
DIR3
DIR2
OE
DIR1
VCC
B2
A2
B4
A4
DIR4
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
0
Ω
TP
TP
TP
TP
Figure 59: 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 35: Component for UART application circuit with partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)