After further reading and comparing multiple Intel datasheets, I have found out some more:
In the datasheet for the ICH4 (Intel DOC 290744), for example, chapter 5.16.8 has nearly (if not completely) the same contents as chapter 12.1.4 in the datasheet for the US15W (Intel DOC 319537). Obviously, the contents of this chapter have been copied-and-pasted between the datasheets for the older chipsets and the datasheets for the newer ones.
Especially, in the ICH4 datasheet, in table 5-75 within the chapter mentioned above, the ominous "Config Register" is also referred to. But in this case, after some searching, one may find that this "Config Register" must be the USB_LEGKEY register which is described in chapter 11.1.16, page 405.
But in the US15W datasheet, there is no such description. This leads to the following two possibilities:
1) In the US15W datasheet, the chapter 12.1.4 (USB Legacy Operation) has been copied-and-pasted from older documents by error. If so, what is the USB legacy behaviour of the US15W, and how can we configure it?
2) The "Config Register" description has been forgotten in the US15W datasheet. I have searched the whole PDF for any sort of substring which may be related to such a register (64WEN, SMIEN and many more), but without success. In this case, where (and when) can we read about this "Config Register"?
Any help appreciated, information urgently needed...
Welcome to the Intel® Embedded Community.
Since you are using Intel® US15W System Controller Hub, I want to make you aware of a special place to go with your technical questions. The Intel e-Help desk is staffed by Intel representatives dedicated to answering embedded Intel® architecture product, design and development questions for select Intel processors, including Atom and US15W.
The Intel e-Help desk is only available to registered private users. Before you can access e-Help, you will first have to upgrade your community membership to private status. Private account status also allows you to access special documents and tools at the Intel® Embedded Design Center. Note that it usually takes a few days for the approval process, and it normally requires that your company has a Non-Disclosure Agreement (NDA) with Intel. If you are interested, Click here to go to your ‘My Account’ page and request registered private access.
In the meantime, let's see if someone in the community can help you with an answer.