Generating Pci Interrupt Acknowledge Cycles; Endian Conversion; When Mpc Devices Are Big-Endian - Motorola MVME2600 Series Reference Manual

Raven PCI Host Bridge & Multi-Processor Interrupt Controller Chip

Generating PCI Interrupt Acknowledge Cycles

2

Endian Conversion

When MPC Devices are Big-Endian

2-16
Performing a read from the PIACK register will initiate a single PCI
Interrupt Acknowledge cycle. Any single byte or combination of bytes
may be read from, and the actual byte enable pattern used during the read
will be passed on to the PCI bus. Upon completion of the PCI interrupt
acknowledge cycle, the Raven will present the resulting vector information
obtained from the PCI bus as read data.
The Raven supports both Big- and Little-Endian data formats. Since PCI
is inherently Little-Endian, conversion is necessary if all MPC devices are
configured for Big-Endian operation. The Raven may be programmed to
perform the Endian conversion described below.
When all MPC devices are operating in Big-Endian mode, all data to/from
PCI must be swapped such that PCI looks big endian from the MPC bus's
perspective. This is shown in Figure 2-3.