SIM900D Hardware Design
PIN NAME
I/O DESCRIPTION
DC CHARACTERISTICS
COMMENT
RXD
I
Receive data
TXD
O
Transmit data
RTS
I
Request to send
CTS
O
Clear to send
RI
O
Ring indicator
DCD
O
Data carry detect
DTR
I
Data terminal Ready
VILmax=0.4V
VIHmin=2.4V
VILmin= 0V
VIHmax= 3V
VOHmin= 2.7V
VOLmax=0.1V
VOHmax= 3V
VOLmin= 0V
1.DTR Pin has
been pulled up.
2.RXD should
be pulled up to
3V through a
10k resistor, if
unused.
3. Other pin
unused keep
open.
Debug interface
PIN NAME
I/O DESCRIPTION
DC CHARACTERISTICS
COMMENT
DBG_TXD
O
DBG_RXD
I
Serial interface for
debugging and
firmware
upgrade
VILmax=0.4V
VIHmin=2.4V
VILmin= 0V
VIHmax= 3V
VOHmin= 2.7V
VOLmax=0.1V
VOHmax= 3V
VOLmin= 0V
If unused keep
open.
SIM interface
PIN NAME
I/O DESCRIPTION
DC CHARACTERISTICS
COMMENT
SIM_VDD
O
Voltage supply for SIM card
The voltage can be select by software
automatically either 1.8V or 3V
SIM_DATA
I/O SIM data input/output
SIM_CLK
O
SIM clock
SIM_RST
O
SIM reset
VILmax=0.15 *SIM_VDD
VIHmin=0.85*SIM_VDD
VILmin= 0V
VIHmax= SIM_VDD
VOHmin= SIM_VDD-0.1V
VOLmax=0.1V
VOHmax= SIM_VDD
VOLmin= 0V
All signals of
SIM interface
are protected
against ESD
with a TVS
diode array.
ADC
PIN NAME
I/O DESCRIPTION
DC CHARACTERISTICS
COMMENT
ADC0
I
General purpose analog to
digital converter.
Input voltage range: 0V ~ 2.8V
If unused keep
open
TEMP_BAT
I
For measure the battery
temperature
If unused keep
open.
Pulse Width Modulation
PIN NAME
I/O DESCRIPTION
DC CHARACTERISTICS
COMMENT
SIM900D_HD_V1.02
09.04.2010
20
