SIM900D Hardware Design
sim card present
detection pin,by
“AT+CSDT”, If
unused keep
open
Serial port
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. If RXD pin
not used, it
should be pulled
up to 3V
through a 10k
resistor.
3. Other unused
pins 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 Input voltage range: 0V ~ 2.8V
If unused keep
SIM900D_Hardware Design_V1.04
2010.10.09
20
Содержание SIM900D EVB
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