User's Manual

GSM/GPRS Module Series
M85 Hardware Design
M85_Hardware_Design Confidential / Released 36 / 88
Module
RTC
Core
VBAT
Power Supply
LDO/DCDC
LDO
VRTC
1.5K
Large Capacitance
Capacitor
Figure 16: VRTC is Supplied by a Capacitor
For the choice of a rechargeable or non-chargeable coin-cell battery, 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 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).
NOTE