MPC555
/
MPC556
BURST BUFFER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
4-2
Figure 4-1 Burst Buffer Block Diagram
4.2 Burst Buffer Features
The BBC offers the following features:
• Supports pipelined access to internal memory and burstable access to the exter-
nal memory.
• Supports the de-coupled interface with the RCPU instruction unit.
• Serves as parked master on the U-bus, resulting in zero clocks delay for RCPU
fetch access to cross to the U-bus.
• Full utilization of the U-bus pipeline for fetch accesses.
• Tightly interfaced with L2U interface module, taking advantage of full U-bus band-
width and back-to-back accesses.
• Supports program trace and show cycle attributes.
• Supports special attribute for debug port fetch accesses.
• Is programmed using the MPC555 / MPC556
mtspr/mfspr
instructions to/from
implementation specific special-purpose registers.
• Designed for minimum power consumption.
The ICDU offers the following features:
• Instruction code on-line decompression based on a fixed vocabulary (bounded
Huffman) algorithm.
• No need for address translation between compressed and non-compressed ad-
dress spaces — ICDU provides “next instruction address” to the RCPU
• Instruction decompression takes one clock cycle.
• Code decompression is pipelined.
• No performance penalty during sequential program flow execution
IMPU
BBC
In-Page Access
Protection-Abort to U-bus
RCPU
U-bus
InstructionAddress Bus
ICDU--Decompressor
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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