Functional Description
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The PCI interface may operate at any clock speed up to 33 MHz. The
PCLK input must be externally synchronized with the MCLK input, and
the frequency of the PCLK input must be exactly half the frequency of the
MCLK input.
PCI Address Mapping
Raven provides three resources to PCI:
❏
Configuration registers mapped into PCI Configuration space
❏
MPC bus address space mapped into PCI Memory space
❏
RavenMPIC control registers mapped into either PCI I/O space or
PCI Memory space
Configuration Registers:
The Raven does not have an IDSEL pin. An internal connection is made
within the Raven that logically associates the assertion of IDSEL with the
assertion of AD31.
Raven provides a configuration space that is fully compliant with the PCI
Local Bus Specification 2.0 definition for configuration space. There are
two base registers within the standard 64-byte header that are used to
control the mapping of RavenMPIC. One register is dedicated to mapping
RavenMPIC into PCI I/O space, and the other register is dedicated to
mapping RavenMPIC into PCI Memory space. The mapping of MPC
address space is handled by device specific registers located above the 64
byte header. These control registers support a mapping scheme that is
functionally similar to the PCI-to-MPC mapping scheme described in
MPC Bus Address Space:
The Raven will map MPC address space into PCI Memory space using
four programmable map decoders. The most significant 16 bits of the PCI
address is compared with the address range of each map decoder, and if the
address falls within the specified range, the access is passed on to the MPC
bus. An example of this is shown in