DSB45 Development Support Box
Confidential / Released
s
DSB45_HD_V05
Page 19 of 50
01.02.2008
2.7.3
Application interface 1 (COM1)
The 1
st
application interface COM1 (X201) of the DSB45 is intended for the communication
between the GSM module and the host application. This RS-232C interface is a data and
control interface for transmitting GPRS data, AT commands, CSD (Circuit Switched Data)
and providing multiplexed channels etc. All modem status lines are available. The interface is
accessible if the slide switches X108 – X115 are set to position “Internal”.
A level converter adapts and inverts the V.24 signals (2.65V level) from the GSM module to
RS-232C level.
The output lines are switched off (high-impedance) if the GSM module is in POWER DOWN
mode. After activating the module via IGT signal (ignition), the serial output lines are
undefined for max. 300 ms, for more details refer to [2].
Table 6: Pin assignment of 1
st
application interface COM1 (X201)
Pin no.
Designation
I/O
Function
1
DCD0
O
Data Carrier Detected 0
2
RXD0
O
Receive Data 0
3
TXD0
I
Transmit Data 0
4
DTR0
I
Data Terminal Ready 0
Note: The ignition signal of the GSM module is activated also
via low-high edge at DTR0 COM1 line
5 GND
-
Ground
6
DSR0
O
Data Set Ready 0
Attention: Switch DSR0_I (X122) must be set to DSR0_I
position.
7
RTS0
I
Request To Send 0
8
CTS0
O
Clear To Send 0
9
RING0
O
Ring Indication 0
Attention: Switch RING0_I (X121) must be set to RING0_I
position.
