82802AB datasheet(29/53 Pages) INTEL

29 / 53 page

Intel

® 82802AB/AC Firmware Hub

Datasheet

4.11.2.

Initializing the RNG Device

Once the RNG device is detected, it must be enabled and should be tested before use.

Step 1:

The RNG Enabled bit (bit 0) of the Hardware Status register must be set to enable the

RNG device.

Step 2:

Once the RNG is enabled, an initial read of the RNG Data register should be made to

clear any preexisting data from the register.

Step 3:

A test (e.g., FIPS 140-1) should be run on the RNG Device. This test will ensure that

there was no error in detecting the device and that the device is functioning properly.

4.11.3.

Selecting Appropriate FWH IDs and Densities

It is possible, using different ID strapping, to use multiple FWH components in a system. While the

FWH protocol supports up to 16 FWH devices, the BIOS support, bus loading or the attaching bridge

may limit this number. Note that, regardless of the number of FWH components, the maximum

“window” of the FWH array visible at one time is 4 MB (for Intel® ICH1) and 8MB for Intel® ICH2. The

boot device must have an ID (as determined by ID [0:3]) of 0. For clarity, it is advisable that subsequent

devices use incremental numbering.

The most straightforward method of using multiple FWH components is to use devices of equal density.

This is the recommended technique.

In special applications, when it is desirable to use multiple FWH components of different densities—if

multiple RNGs or more GPIs are required, for instance, without the need for greater array space—IDs

must be chosen such that component memory array spaces do not cross the boundaries delimited by the

highest-capacity device, as illustrated in the following table.

For example, in a design with 8- and 4-Mbit components, the 8-Mbit part must either be first or must be

after enough 4-Mbit parts to add up to a multiple of 8 Mbits.

Yes

8 Mbits

4 Mbits

8 Mbits

4 Mbits

8 Mbits

Biggest is

8 Mbits.

82802AB Datasheet(PDF) 29 Page - Intel Corporation