Hardware Design V1.01(091226)

SIM900 Hardware Design
pad to SIM card
holder.
SIM_PRESE
NCE
I SIM detect VILmax=0.15 *VDD_EXT
VIHmin=0.85*VDD_EXT
VILmin= 0V
VIHmax= VDD_EXT
If unused keep
open
ADC
PIN NAME I/O DESCRIPTION DC CHARACTERISTICS COMMENT
ADC I General purpose analog to
digital converter.
Input voltage range: 0V ~ 3V If unused keep
open
External Reset
PIN NAME I/O DESCRIPTION DC CHARACTERISTICS COMMENT
NRESET I External reset input(Active
low)
VILmax=0.15 *VDD_EXT
VIHmin=0.85*VDD_EXT
VILmin= 0V
VIHmax= VDD_EXT
If unused keep
open
Pulse Width Modulation
PIN NAME I/O DESCRIPTION DC CHARACTERISTICS COMMENT
PWM1 O PWM Output
PWM2 O PWM Output
VOHmin= VDD_EXT-0.1V
VOLmax=0.1V
VOHmax= VDD_EXT
VOLmin=0
If unused keep
open
3.2 Operating Modes
The table below briefly summarizes the various operating modes referred to in the following chapters.
Table
6: Overview of operating modes
Mode Function
GSM/GPRS
SLEEP
Module will automatically go into SLEEP mode if DTR is set to high level
and there is no on air and no hardware interrupt (such as GPIO interrupt or
data on serial port).
In this case, the current consumption of module will reduce to the minimal
level.
In SLEEP mode, the module can still receive paging message and SMS
from the system normally.
Normal
operation
GSM IDLE Software is active. Module has registered to the GSM network, and the
SIM900_HD_V1.01 26.12.2009
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