Specifications

AC65/AC75 Hardware Interface Description

3.10 Serial Interface ASC0

AC65_AC75_HD_v01.002 Page 51 of 117 2006-10-30

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3.10 Serial Interface ASC0

AC65/AC75 offers an 8-wire unbalanced, asynchronous modem interface ASC0 conforming to ITU-T V.24 pro-

tocol 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 2.9V (for high data bit or inactive state). For electrical characteristics please

refer to Table 26.

AC65/AC75 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 16: 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 primarily designed for controlling voice calls, transferring CSD, fax and GPRS data and for controlling

the GSM engine with AT commands.

• Full Multiplex capability allows the interface to be partitioned into three virtual channels, yet with CSD and fax

services only available on the first logical channel. Please note that when the ASC0 interface runs in Multiplex

mode, ASC1 cannot be used. For more details on Multiplex mode see [12].

• The DTR0 signal will only be polled once per second from the internal firmware of AC65/AC75.

• The RING0 signal serves to indicate incoming calls and other types of URCs (Unsolicited Result Code). It can

also be used to send pulses to the host application, for example to wake up the application from power saving

state. See [1] for details on how to configure the RING0 line by AT^SCFG.

• By default, configured for 8 data bits, no parity and 1 stop bit. The setting can be changed using the AT com-

mand AT+ICF and, if required, AT^STPB. For details see [1].

• ASC0 can be operated at fixed bit rates from 300 bps to 460,800 bps.

• Autobauding supports bit rates from 1,200 to 460,800 bps.

• Autobauding is not compatible with multiplex mode.

• Supports RTS0/CTS0 hardware flow control and XON/XOFF software flow control.