User's Manual

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EHS6-A Hardware Interface Overview Page 14 of 41

2.1 Application Interface

 EHS6-A_HIO_v02.770 2014-08-13

Confidential / Preliminary

2.1.2 Serial Interface ASC0

EHS6-A offers an 8-wire unbalanced, asynchronous modem interface ASC0 conforming to

ITU-T V.24 protocol DCE signalling. The electrical characteristics do not comply with ITU-T

V.28. The significant levels are 0V (for low data bit or active state) and 1.8V (for high data bit

or inactive state).

EHS6-A 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: • Port TXD

@ application sends data to the module’s TXD0 signal line

• Port RXD @ application receives data from the module’s RXD0 signal line

Figure 3: Serial interface ASC0

Features:

• Includes the data lines TXD0 and RXD0, the status lines RTS0 and CTS0 and, in addition,

the modem control lines DTR0, DSR0, DCD0 and RING0.

• ASC0 is designed for controlling GSM/UMTS voice calls, transferring data and for

controlling the module with AT commands.

• Full multiplexing capability allows the interface to be partitioned into virtual channels.

• The RING0 signal serves to indicate incoming calls and other types of URCs (Unsolicited

Result Code). It can also be used to send p ulses to the host application, for example to

wake up the application from power saving state.

• Configured for 8 data bits, no parity and 1 stop bit.

• ASC0 can be operated at fixed bit rates from 1,200bps up to 921,600bps.

• Autobauding supports bit rates from 1,200bps up to 230,400bps.

• Supports RTS0/CTS0 hardware flow control. The hardware hand shake line RTS0 has an

internal pull down resistor causing a low level signal, if t he line is n ot used and open.

Although hardware flow control is recommended, this allows communication by using only

RXD and TXD lines.

• Wake up from SLEEP mode by RTS0 activation (high to low transition).

2.1.3 Serial Interface ASC1

Four EHS6-A GPIO lines can be configured as ASC1 interface signals to provide a 4-wire

unbalanced, asynchronous modem interface ASC1 conforming to ITU-T V.24 protocol DCE

signalling. The electrical characteristics do not comply with ITU-T V.28. The significant levels

are 0V (for low data bit or active state) and 1.8V (for high data bit or inactive state).