Operating Your MultiModemZDX

2 - Installation

You control your MultiModemZDX by issuing AT commands and setting S-Registers. Right now your MultiModemZDX is set up for the most typical user application, that is, as a traditional modem set to make a dial-up call to a remote installation where the call is answered automatically; therefore, you shouldn’t need to change the current default configuration. (If however, you know that your application does not follow this profile, please refer to Chapter 3 for AT Commands and S-Registers.)

In operating your MultiModemZDX it is likely that you will use your data communications software to either:

•enter “terminal” mode, where you can “speak most directly” to the modem by issuing AT commands, or to

•launch a datacomm session through a set of modem configurations which you select and then associate with a target telephone number. Once you have created, saved, and named this set of information according to your connection needs and your datacomm software’s conventions, the software then simplifies your dialing because you needn’t reconfigure your modem, nor run the risk of mistakenly keying-in incorrect information.

Either way, you need to understand that an AT command is the method by which your modem is controlled, and must therefore prefix nearly all commands. AT stands for attention, and alerts the modem that a command follows. You may enter these commands with either upper- or lower-case characters. Entering AT automatically sets the modem’s serial baud rate to match your computer’s and also sets the modem’s parity. It also clears the modem’s command buffer. Once you’re in terminal mode, enter AT followed by <CR> to check whether your modem is operational. If everything’s fine, your modem will respond OK.

Simple Operations

You can dial by using the ATD command and the phone number of the modem with which you wish to connect, e.g., ATD6127853500. Your modem will dial the number; a “scrambling” noise is heard as the modem negotiates the kind of connection it can make, and once the modems have settled on a common connection, a connect message on your computer’s video is displayed. To hang up a call, enter +++ATH<CR>. Your modem will return on hook, just as if you had returned a phone’s handset to its cradle. Your video now displays OK, signifying that your modem is ready for your next command.