Functional Description
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The CONFIG_ADDRESS and CONFIG_DATA registers are actually
represented in PCI space to the processor and are subject to the Endian
functions. For example, the powerup location of the CONFIG_ADDRESS
register with respect to the PPC bus is $80000cf8 when the PHB is in Big-
Endian mode. When the PHB is switched to Little-Endian mode, the
CONFIG_ADDRESS register with respect to the PPC bus is $80000cfc.
Note that in both cases the address generated internal to the processor wi ll
be $80000cf8.
The contents of the CONFIG_ADDRESS register are not subject to the
Endian function.
The data associated with PIACK accesses is subject to the Endian
swapping function. The address of a PIACK cycle is undefined; therefore,
address modification during Little-Endian mode is not an issue.
Error Handling
The PHB is capable of detecting and reporting the following errors to one
or more PPC masters:
XBTO - PPC address bus time-out
XDPE - PPC data parity error
PSMA - PCI master signalled master abor t
PRTA - PCI master received target abort
PPER - PCI parity error
PSER - PCI system error
Each of these error conditions will cause an error status bit to be set i n the
PPC Error Status Register (ESTAT). If a second error is detected while any
of the error bits is set, the OVFL bit is assert e d, but none of the error bits
are changed. Each bit in the ESTAT may be cleared by writing a 1 to it;
writing a 0 to it has no effect. New error bits may be set only when all
previous error bits have been cleared.