HP XM600 - Kayak - 128 MB RAM Technical Reference Manual page 63

The FWH includes two hardware interfaces:
FirmWare Hub interface.
•
Address/Address Multiplexed (A/A Mux) interface.
•
The IC (Interface Configuration) pin on the FWH provides the control
between these interfaces. The interface mode needs to be selected prior to
power-up or before return from reset (RST# or INIT# low to high
transition).
The FWH interface works with the ICH during system operation, while the
A/A Mux interface is designed as a programming interface for component
pre-programming.
An internal CUI (Command User Interface) serves as the control center
between the FWH and A/A Mux interfaces, and internal operation of the
non-volatile memory. A valid command sequence written to the CUI initiates
device automation. An internal WSM (Write State Machine) automatically
executes the algorithms and timings necessary for block erase and program
operations.
2 System Board
FirmWare Hub (82802AA)
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