GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 32 / 80
Module
RTC
Core
VBAT
Power Supply
LDO/DCDC
LDO
VRTC
1.5K
Large Capacitance
Capacitor
Figure 13: VRTC is Supplied by a Capacitor
A rechargeable or non-chargeable coin-cell battery can also be used here, for more information, please
visit http://www.sii.co.jp/en/.
If you want to keep an accurate real time, please keep the main power supply VBAT alive.
3.7. Serial Interfaces
The module provides three serial ports: UART Port, Debug Port and Auxiliary UART Port. The module is
designed as a DCE (Data Communication Equipment), following the traditional DCE-DTE (Data Terminal
Equipment) connection. Autobauding function supports baud rate from 4800bps to 115200bps.
The UART Port:
TXD: Send data to RXD of DTE.
RXD: Receive data from TXD of DTE.
RTS: Request to send.
CTS: Clear to send.
DTR: DTE is ready and inform DCE (this pin can wake the module up).
RI: Ring indicator (when there is a call, SMS or URC output, the module will inform DTE with the RI
pin).
DCD: Data carrier detection (the validity of this pin demonstrates the communication link is set up).
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