SIM5218E Hardware Design
SIM5218E_ Hardware Design_V1.06
2012.09.21
24
of SIM5218E is connected with a host CPU , SIM5218E can not enter sleep mode until
SIM5218E RXD is pulled down by the host CPU . When module is in idle mode, one can pull
the module RXD to low level by the host CPU TXD. We suggest using UART_RI to inform or
wake up the host CPU (please refer to serial interface
section ).
3. RXD is pulled down by 15k ohm inside SIM5218E. Please don’t connect if RXD is not
used.
4. Please reference SIM52xx_Sleep_Mode_Application_Note for detailed information of
_Sleep_Mode.
3.5.4 Wake up SIM5218E from Sleep Mode
When SIM5218E is in SLEEP mode, the following methods can wake up the module.
z
USB interface active
z
Receive a voice or data call from network to wake up SIM5218E.
z
Receive a SMS from network to wake up SIM5218E.
z
Receive a interrupt signal from GPIO0
z
GPIO4 state change.
z
Receive AT command from UART.
z
UART DTR signal changed.
Normally DTR pin will stay high but in certain condition
when
serial port is used in Null
Modem(3-line mode). When host wants to wake up SIM5218E, it can pull down DTR for about
12ms(since SIM5218E has a debounce time of 10ms for mistaken interrupt checking). Then DTR
will trigger an interrupt which will finally cause SIM5218E to be waken up from sleep mode.
Note: One can enable/disable such function by AT+CDTRISRS, also One can configure the
DTR’s trigger condition by AT+CDTRISRMD(only level trigger condition has debounce time).
Currently the function is enabled by default and the trigger condition is low level. Please
reference document [23] for detailed information of Waking_up_Application_Note.
WARNING!!!: when DTR has been pulled down/up long enough to trigger the interrupt one
must recover DTR to original status or the interrupt will be triggered all the time and
SIM5218E may crash.
3.6 RTC backup
The RTC (Real Time Clock) power supply of module can be provided by an external battery or a
battery (rechargeable or non-chargeable) through the VRTC (PIN11) on the board-to-board
connector. User need only a coin-cell battery or a super-cap to VRTC to backup power supply for
RTC. The discharge current is smaller than 10uA.The module could update local time based on
universal time and time zone from network.(This feature must be supported by the network ).If
this feature is used, please refer to AT command AT+CTZU and AT +CTZR.
Note: The VRTC default state can be designed to a NC pin in user’s circuit. If user need to use
