In a message dated 96-05-15 20:10:29 EDT, you write: >Our company is going through the growing pains of its first modem >design with intended sale in Europe starting with the Netherlands. We >have choosen the Rockwell RC224ATL modem chip and our first run >through of our design indicates some weak points, (ie possible >problems) in the dialtone and busytone detection areas. >
Tom: I looked at the Rockwell RC224ATL chip about two years ago for an embedded modem application that had to meet worldwide approval requirements. At that time, my conclusion was that this device did not offer sufficient flexibility in the call progress tone detector. I believe the part was designed for the North American market, and the call progress tone detectors are hard-coded to detect North American tones. You may find that this part works OK in countries where the call progress tones and the cadences are similar to North America, but I do not think this part is a good choice if you plan to sell your product worldwide. In general, a call progress tone detector for worldwide applications should allow you to configure the allowable frequency bandwidth, cadence, and energy threshold for the tones that you are trying to detect. At the time of my investigation, the least expensive Rockwell solution that had the required flexibility was the RC2424DP/1. I ended up using a general purpose DSP instead, so I can't say much more about the RC2424DP/1 except that it appeared to have the required flexibility. I do not know if Rockwell even sells this chip any more. In general, I believe that Rockwell sells their modem chips in two categories. The first type is a "data pump" that implements the basic modem functions and usually offers direct access to the coefficients of the tone detection filters. These devices offer maximum flexibility, but you must add your own microprocessor that implements higher level functions such as the AT command set, data compression, and error correction. The second type is a pre-packaged version that uses one of Rockwell's microprocessors to implement the high level functions. In this second category, the call progress tone detection parameters are usually hard-coded. However, for some members of this family, Rockwell offers a software utility called "ConfigurACE" that lets you modify the parameters used in the call progress tone detector. So, I suggest that you have a detailed discussion with a knowledgeable Rockwell applications engineer, to make sure that the specific Rockwell device you select has the flexibility to accommodate the countries that you wish to cover. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc.
