Motorola IH5, MCPN750A manual Remote Start Via the PCI Bus, Overview

Remote Start Via the PCI Bus

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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 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.

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:

❏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.

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