Application Note
CM L M icrocircuits
COMMUNICATION SEMICONDUCTORS
CMX866 Operation
with Low-Level Commands
AN/Telecom/866/Commands/1 January 2003
1 Introduction
The CMX866 is a V.22bis modem IC that was designed to connect to off-the-shelf
V.22bis-capable modems using industry standard 鈥淎T鈥?commands. Special AT
commands must be used to allow the CMX866 to perform low-level functions such
as DTMF generation and programmable dual tone detection. The purpose of this
application note is to describe how the CMX866 can be made to perform these types
of functions.
1.1 Contents
Introduction ......................................................................................................... 1
1.1
Contents ...................................................................................................... 1
2 Examples ............................................................................................................ 1
2.1
DTMF Generation ........................................................................................ 2
2.2
DTMF Detection........................................................................................... 2
2.3
Programmable Tone Generation ................................................................. 3
2.4
Programmable Tone Detection .................................................................... 5
2.5
Use Of Hook Switch 鈥淎T鈥?Command and the Effect On Impedance
Presented To Telephone Line ................................................................................ 6
3 Conclusion .......................................................................................................... 6
1
2 Examples
The CMX866 can be made to perform a variety of low-level functions with the use of
special AT commands combined with user-defined register values. Once the desired
function(s) has been resolved, the required CMX866 register contents can be
determined. In general, these register contents are loaded into the CMX866 with
special AT commands, and these commands will cause the desired operating mode
to occur.
The CMX866 shares internal register addresses and structure with the CMX868
(V.22bis modem IC without AT command set). Consequently, to determine the
appropriate CMX866 register and setting for a particular operating condition, the
CMX868 data sheet should be consulted. Data sheets for all CML products can be
found at the following internet address:
http://www.cmlmicro.com/products/datasheets/download.htm
CMX866 Operation with Low-Level Commands
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