Table 14: Logic Levels Of Serial Ports Pins - SimCom SIM548C HD V1.01 Hardware Design

SIM548C Hardware Design
The GSM part of the module provides two unbalanced asynchronous serial ports. One is the serial
port and another is the debug port. The GSM part is designed as a DCE (Data Communication
Equipment), following the traditional DCE-DTE (Data Terminal Equipment) connection.The
module and the client (DTE) are connected through the following signal (as following figure
shows). Autobauding supports baud rate from 4800bps to 115200bps.
Serial port
TXD: Send data to the RXD signal line of the DTE
RXD: Receive data from the TXD signal line of the DTE
Debug port
DBG_TXD: Send data to the /RXD signal line of the DTE
DBG_RXD: Receive data from the /TXD signal line of the DTE
The logic levels are described in following table

Table 14: Logic levels of serial ports pins

Parameter
V
IL
V
IH
V
OL
V
OH
SIM548C_HD_V1.01
Min
0
2.1
GND
2.8
45
Max
0.9
3.3
0.2
3
Unit
V
V
V
V
09.05.2008