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5Remote Start Via the PCI Bus
Introduction
This chapter describes the remote interface provided by the firmware to the
host CPU via the cPCI bus. This interface facilitates the host obtaining
information about the board, downloading code and/or data, and execution
of the downloaded program.
Note
Overview
PPCBug uses one of the scratch pad registers of the 2155x PCI-to-PCI
bridge as the command/response channel. This scratch pad register is
logically divided into 5 sections:
Applications may also be downloaded to the MCPN750A via one
of the PCI bus windows provided by the PCI-to-PCI bridge. This
method is faster than using the PPCBug remote interface and may
be preferable to use for large downloads.
An ownership flag. When set, indicates that the host 'owns' the
register and is free to write a new command into it. It also indicates
that the previous command, if any, has been completed and the
results, if any, have been returned to the register. When the host
writes a new command to the register, it must clear the ownership
flag to indicate the register contains a command to be processed.
A 'command opcode'. This field is a numeric field which specifies
the command the host desires to be performed.
An error flag which is used to provide command completion status
to the host CPU.
A 'command options' field. This field further qualifies the specifics
of the command to be performed. The meaning of the option field is
specific to each command opcode.
5
5-1
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