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Functional Description
3
The Raven bridge controller ASIC provides the bridge between the
MPC750 microprocessor bus and the PCI local bus. Electrically, the Raven
chip is a 64-bit PCI connection. Four programmable map decoders in each
direction provide flexible addressing between the MPC750
microprocessor bus and the PCI local bus.
Flash Memory
The MCP750 base board has provision for 1MB of 16-bit Flash memory
in two 8-bit sockets. The RAM300 memory mezzanine accommodates
4MB or 8MB of additional 64-bit Flash memory.
The onboard monitor/debugger, PPCBug, resides in the Flash chips.
PPCBug provides functionality for:
❏
Booting the operating system
❏
Initializing after a reset
❏
Displaying and modifying configuration variables
❏
Running self-tests and diagnostics
❏
Updating firmware ROM
Under normal operation, the Flash devices are in “read-only” mode, their
contents are pre-defined, and they are protected against inadvertent writes
due to loss of power conditions. However, for programming purposes,
programming voltage is always supplied to the devices and the Flash
contents may be modified by executing the proper program command
sequence. Refer to the third-party data sheet and/or to the PPCBug
Firmware Package User’s Manual (PPCBUGA1/UM and
PPCBUGA2/UM) for further device-specific information on modifying
Flash contents.
RAM300 Memory Module
The RAM300 is the ECC DRAM memory mezzanine module that
(together with an optional PCI mezzanine card) plugs into the base board
to make a complete MCP750 single-board computer. See
Chapter 1,
Hardware Preparation and Installation
.