82802AB datasheet(30/53 Pages) INTEL

30 / 53 page

Intel

® 82802AB/AC Firmware Hub

Datasheet

4.11.4.

Mapping FWH Devices onto Memory Map

There is 4 MB of available memory space devoted to the FWH. Therefore, the Intel ICH has the ability

to select which FWH device maps into each region of the system address space.

In the existing Intel ICH, the address map is broken up into eight 512-KB segments. The BIOS Select

determining which FWH receives requests from which portion of the address map. For example, in a

system with four 8-Mbit devices, this register would be 00112233h, which is the default power-up state

for this register. In a system with eight 4-Mbit devices, the register must be changed to 01234567h.

Note: The FWH indicated in the most-significant nibble of the register may be shadowed elsewhere in the

system memory map. The FWH with ID 0 may not be re-mapped.

4.11.5.

Paging FWH Devices for Greater Than 4 MB of FWH Memory

In certain applications, even a 4-MB window of flash memory is inadequate. It is possible to exceed this

amount by using a paging scheme. Individual FWH devices may then be “swapped” in and out of system

memory space. This must be implemented at the BIOS level, to permit modification of the Intel ICH

BIOS Select Register. A number of paging algorithms may be used successfully with the FWH memory

space, using the Intel ICH BIOS Select Register. This register, then, determines which FWH device gets

mapped into each 512 KB “slice” of the system memory map. The 0th FWH (ID=0) may not be

remapped. Reference the Intel® 82801AA (ICH) and Intel® 82801AB (ICH0) I/O Controller Hub

Datasheet (order number: 290655) for information regarding these components and the BIOS Select

Note: The paging of FWH devices will also “page” features, potentially affecting the visibility or location of

the FGPI register (see Section 4.9.2.1) or of an active/ready RNG. When a paging scheme is used, it is

recommended that critical FPGIs be used only on the ID 0 FWH device, which must remain mapped at

the top of memory. Ideally, the RNG driver in a system with more than four FWHs should verify the

mapping of FWHs in order to keep track of which RNGs are active and which are present in the memory

map. There is no convenient way, aside from checking the select register, to determine which IDed FWH

is in which location in the memory map.

4.11.6.

Programming Multiple FWH Devices

Special considerations must be taken into account when programming multiple FWH devices in-system.

Since there is no ID support in the A/A Mux mode, the recommended means of programming multiple

devices is either out-of-system programming with standalone PROM programmers or in-system

programming using the FWH mode. In cases where programming time is critical or ATE programming is

required, provisions should be made to isolate the component from its neighboring devices during A/A

Mux programming, or the other devices should be held in a reset (or otherwise disabled) state until

programming of the intended device is complete. Do not switch one component into the A/A Mux mode,

thereby leaving the others in the FWH mode.

82802AB Datasheet(PDF) 30 Page - Intel Corporation