Unlike the one for Copper Mountain SDSL, the SDSL/ATM wanlet appears to have been designed by Netopia themselves. The functional design is markedly different from CM's: the bitpump is an RS8973 with a custom 10.240 MHz crystal for the built-in multirate symbol clock synthesiser, and a completely different microprocessor subsystem is used. However, even as the newer bitpump is used, I couldn't help but notice that the line transformer, the surge protection design and the slightly modified line interface circuit are exactly the same as on the CM module: CM must have allowed Netopia to copy these aspects for the non-CM flavors. (It is far from certain though that the Midcom 50051 transformer optimised for 784 kbps is optimal for the Nokia SDSL symbol rates...)
Besides the RS8973 with its suspiciously-cloned line interface, the wanlet features a Virata Helium VC8410 processor, a soldered TSOP flash chip with firmware, an Altera EPF6016ATC100 FPGA and an EPM7032AE CPLD.
We know that this processor has an ARM core because it says so on the chip,
but that's unfortunately all that can be found out about this chip.
The name Virata
should ring a bell: it's the second half of
GlobespanVirata which we have already encountered when looking into the
Orion S(H)DSL chipset.
That chipset had apparently come from the Globespan half, and now we are
looking at something from the Virata half.
Extensive Google searches have turned up no information about this chip except that it has been used in some ADSL products as well. Given that it comes from a telecom company, we can safely assume that it was specifically designed as a telecom processor (perhaps competing with the PowerQUICC family from Motorola/Freescale), and seeing this chip appear in an SDSL/ATM module and in ADSL (also ATM) products, we can make an educated guess that it probably has ATM functions, perhaps a UTOPIA host interface.
The unfortunate part is that it would be extremely difficult to obtain any technical information about this processor. Whether it was Globespan or Virata, GlobespanVirata has been acquired by Conexant, which appears to be a rather clam-tight company. The chip is probably long obsolete and discontinued, and Conexant would have no incentive to dig in their historical archives for us.
This news is unfortunate from the perspective of reverse-engineering the SDSL/ATM module for the details of the SDSL flavors it implements. Trying to reverse-engineer a module which consists of nothing but a totally unknown processor and a bunch of programmable logic would be like reverse-engineering a UFO.
How does the SDSL/ATM wanlet present the data payload to the UMB3 motherboard's MC68MH360 processor? Do they use RAM-based CPM microcode for serial ATM on the MC68MH360, or does the ARM/FPGA/CPLD trio on the wanlet perform Layer 2 conversion from ATM to HDLC? Again given that proper reverse engineering would be prohibitively difficult, we can only guess.
From some old Netopia release notes it appears that the wanlet was
originally designed for the Nokia
flavor but then extended to generic
Flavor A.
On our R7200 the configuration menu gives several DSLAM names (including Nokia)
plus Generic
.
Our experiments using the Hack-o-Rocket
have revealed that all profiles other than Nokia correspond to Flavor A
with either SSS or no scrambling at the I.432.1 level.
There does not appear to be any support for HTU-C mode operation, only HTU-R (CPE).