Baudman's August Q&As

The Different Rockwell Modem Chipsets

Weed> There are, in fact, many "ROCKWELL" chip-sets which are
Weed> capable of FAX/Modem operation.
[...]
Weed> Reply-er's to newsgroup questions must be careful when
Weed> discussing Rockwell chips; [...]

I liked your initial statement and where I thought you were going with this post... but as the text progressed... focus and accuracy diminished...

This will be a very general (and unofficial!) overview. For the purpose of discussion, let's assign a complete modem that is sitting on the shelf in a store the value of 100% implementation. Let's call a Digital Signal Processor (DSP) chip with no firmware/software associated with it a 0% implementation. Rockwell offers three broad product lines in between those extremes: 1) Socket Modems, 2) Integrated chipsets, and 3) DataPumps.

Very rough approximations of "modem implementation" percentage would be something like the following:

The DP products basically have 2 main components inside of the chip. One is the Digital Signal Processor (DSP) itself. There is masked ROM in the device which stores the "program" for doing all of the basic modulations (V.34, V.32bis, etc). The other important part is called the "Integrated Analog" or IA... which basically performs the Analog-to-Digital and Digital-to-Analog conversions and associated filtering. Products in this group include parts such as the RC288DPi (for V.34 and "below") and RC144DPi (for V.32bis and "below").

The interfaces for those chips are oriented towards low level control... they do not have the ability to be controlled by sending "AT commands" to them. Since users (and COMM programs) would like to have a "nicer" interface and more abstraction... a final product almost always implements an "AT command" interface. That interface is implemented on a microcontroller running controller firmware. With the addition of memory (RAM) that controller can also run modem protocols (V.42bis, MNP, etc ) as opposed to the modem modulations (V.34, V.32bis) implemented in the DataPump.

Rockwell also manufactures microcontrollers in addition to Data Pumps. The microcontrollers could have a number like C29, C39, C40, etc. When Rockwell sells a microcontroller with the DataPump it is refered to as an AC or "integrated" chipset. Typical products include RC144ACi and RC288ACi. Unlike the DataPumps, the microcontrollers do NOT have the controller code burned into the device... a seperate external memory device like an EPROM or FlashROM is used. (More on what code goes into the device later...)

A manufacturer may choose to use a third-party microcontroller and do all of the controller and protocol programming themselves.

Even with a "Integrated Chipset", a manufacture still has a long way to go before having an approvable and sellable modem. There are 2 main interfaces that also must be included. The first is the "computer" interface. The modem must somehow be connected to the computer so the appropriate (ISA) bus or port (serial or parallel) interface components must be used. At the "other end" of the chipset, the analog portion of the chipset must be connected to the telephone jack through something called a Data Access Arrangement (DAA). Design of a DAA is non-trivial... attention must be paid to part selection, noise, safety issues, temperature effects, etc.

Rockwell's SocketModem line of products integrates those interfaces and an "integrated" chipset and sometimes RAM/ROM into a single 1 inch by 2.5 inch (2.5 cm x 6 cm) printed circuit board module. Product examples include the SMV144AC, SM96V24AC, and SM224ATF families which are all pin compatible. In some cases, all that is needed is a few additional (trivial) components to make a final modem. (Note: typically, SocketModems are not the Rockwell product line a "inexpensive no-name" modem would use... an "integrated" chipset often offers more manufacturing/economic efficiencies.)

Rockwell offers several forms of technical support for manufacturers who use Rockwell products. Some of those items include data sheets, application notes, Designer's Guides, and AccelerATor kits. An AccelerATor kit includes all kinds of design information and examples including Rockwell controller code for the integrated chipset. Although a modem could be built verbatim with the design information in the AccelerATor kit, that modem would probably not be very competitive in today's market... so the manufacturer will redesign/refine the modem hardware and firmware. Some manufacturers who use the integrated modems make substantial additions and changes to the Rockwell firmware.

Anyways, hopefully that gives you somewhat of an idea of Rockwell's product offerings and how the performance/features/price/etc of a modem "with a Rockwell chip in it" varies greatly. IE, refering back to the original poster, it is important to realize what level of Rockwell product is being used in a "Rockwell Modem" [sic.]

Which modem uses RPI