SIM Tech SIM900D HD Manual page 20

SIM900D Hardware Design
PIN NAME I/O DESCRIPTION
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
Debug interface
PIN NAME I/O DESCRIPTION
DBG_TXD O Serial
debugging
upgrade
DBG_RXD I
SIM interface
PIN NAME I/O DESCRIPTION
SIM_VDD O Voltage supply for SIM card
SIM_DATA I/O SIM data input/output
SIM_CLK O SIM clock
SIM_RST O SIM reset
ADC
PIN NAME I/O DESCRIPTION
ADC0 I General purpose analog to
digital converter.
TEMP_BAT I For
temperature
Pulse Width Modulation
PIN NAME I/O DESCRIPTION
SIM900D_HD_V1.02
DC CHARACTERISTICS
VILmax=0.4V
VIHmin=2.4V
VILmin= 0V
VIHmax= 3V
VOHmin= 2.7V
VOLmax=0.1V
VOHmax= 3V
VOLmin= 0V
DC CHARACTERISTICS
interface for VILmax=0.4V
and firmware VIHmin=2.4V
VILmin= 0V
VIHmax= 3V
VOHmin= 2.7V
VOLmax=0.1V
VOHmax= 3V
VOLmin= 0V
DC CHARACTERISTICS
The voltage can be select by software
automatically either 1.8V or 3V
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
measure the battery
20
DC CHARACTERISTICS
Input voltage range: 0V ~ 2.8V
DC CHARACTERISTICS
COMMENT
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.
COMMENT
If unused keep
open.
COMMENT
All signals of
SIM interface
are protected
against ESD
with a TVS
diode array.
COMMENT
If unused keep
open
If unused keep
open.
COMMENT
09.04.2010