Motorola MVME2400 Series Service Manual Page 87

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Functional Description
http://www.mcg.mot.com/literature 2-29
2
Parity:
The PCI Master supports address parity generation, data parity generation,
and data parity error detection.
Cache Support:
The PCI Master does not participate in the PCI caching protocol.
Generating PCI Cycles
There are four basic types of bus cycles that can be generated on the PCI
bus:
Memory and I/O
Configuration
Special Cycle
Interrupt Acknowledge
Generating PCI Memory and I/O Cycles
Each programmable slave may be configured to generate PCI I/O or
memory accesses through the MEM and IOM fields in its XSATTx
register as shown below.
:
If the MEM bit is set, the PHB performs Memory addressing on the PCI
bus. The PHB takes the PPC bus address, applies the offset specified in the
XSOFFx register, and maps the result directly to the PCI bus.
The IBM CHRP specification describes two approaches for handling PCI
I/O addressing: contiguous or spread address modes. When the MEM bit
is cleared, the IOM bit is used to select between these two modes whenever
a PCI I/O cycle is to be performed.
MEM IOM PCI Cycle Type
1xMemory
0 0 Contiguous I/O
0 1 Spread I/O
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