Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 35 / 82
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).
NOTE