Hardware Design V1.01(091226)
Table Of Contents
- Contents
- Version history
- 1 Introduction
- 2 SIM900 Overview
- 3 Application Interface
- 3.1 SIM900 Pin Description
- 3.2 Operating Modes
- 3.3 Power Supply
- 3.4 Power Up and Power Down Scenarios
- 3.5 Power Saving
- 3.6 Summary of State Transitions (except SLEEP mode)
- 3.7 RTC Backup
- 3.8 Serial Interfaces
- 3.9 Audio Interfaces
- 3.10 SIM Card Interface
- 3.11 LCD Display Interface
- 3.12 Keypad Interface
- 3.13 ADC
- 3.14 Behaviors of the RI
- 3.15 Network Status Indication
- 3.16 General Purpose Input Output (GPIO)
- 3.17 External Reset
- 3.18 PWM
- 3.19 I2C Bus
- 4 Antenna Interface
- 5 Electrical, Reliability and Radio Characteristics
- 6 Mechanics
SIM900 Hardware Design
3.4.2.1 Turn Off SIM900 Using the PWRKEY Pin (Power down)
You can turn off the SIM900 by driving the PWRKEY to a low level voltage for a short time and then release. You
also can urn off the SIM900 by connecting PWRKEY and PWRKEY_OUT for a short time and then release.
Please refer to the turn on circuit. The power down scenario illustrates as following figure.
This procedure lets the module log off from the network and allows the software to enter into a secure state and
save data before completely disconnecting the power supply.
Before the completion of the switching off procedure the module will send out result code:
NORMAL POWER DOWN
After this moment, the AT commands can’t be executed. The module enters the POWER DOWN mode, only the
RTC is still active. POWER DOWN can also be indicated by STATUS pin, which is a low level voltage in this
mode.
Figure 12: Timing of turn off system using PWRKEY
SIM900_HD_V1.01 26.12.2009
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