82802AB Datasheet, PDF (29/53 Pages) Intel Corporation – Firmware Hub (FWH)

Intel^® 82802AB/AC Firmware Hub
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4.11.2. Initializing the RNG Device
4.11.3.
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.
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
No
4 Mbits
8 Mbits
Yes
4 Mbits
4 Mbits
8 Mbits
Biggest is 8 Mbits.
Datasheet
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