User's Manual

MC46 Hardware Interface Description
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MC46_HD_V03.05 Page 48 of 99 13.11.2003
3.9 Serial interfaces
MC46 offers two unbalanced, asynchronous serial interfaces conforming to ITU-T V.24
protocol DCE signaling. The electrical characteristics do not comply with ITU-T V.28. The
significant levels are 0V (for low data bit or ON condition) and 2.65V (for high data bit or OFF
condition). For electrical characteristics please refer to Table 38.
The GSM engine is designed for use as a DCE. Based on the conventions for DCE-DTE
connections it communicates with the customer application (DTE) using the following
signals:
ASC0
· Port /TXD @ application sends data to the module’s /TXD0 signal line
· Port /RXD @ application receives data from the module’s /RXD0 signal line
ASC1
· Port /TXD @ application sends data to module’s /TXD1 signal line
· Port /RXD @ application receives data from the module’s /RXD1 signal line
GSM module
Application
/TXD
/RXD
/RTS
/CTS
/RING
/DCD
/DSR
/DTR
/TXD
/RXD
/RTS
/CTS
1
st
serial interface
(DTE)
(DCE)
2
nd
serial interface
ASC0 interface
ASC1 interface
/TXD0
/RXD0
/RTS0
/CTS0
/RING0
/DCD0
/DSR0
/DTR0
/TXD1
/RXD1
/RTS1
/CTS1
Figure 15: Serial interfaces