MSC8144E Reference Manual, Rev. 3
11-2
Freescale
Semiconductor
Internal Memory Subsystem
11.1
Memory Management Unit (MMU)
The MMU provides a high-speed address translation mechanism to enable memory relocation,
and checks access permissions for core instructions and data buses. It also controls hardware task
protection and provides cache and bus controls for advanced memory management. The MMU
enables better integration of system resources and defines a cleaner software model. For example,
programing protected regions, address translation regions, cacheable regions, and so on can be
combined. In addition, cache usage can be optimized based on the specific attributes controlled
by the MMU programming. For memory protection, the MMU enables the implementation of an
RTOS with MMU support, thereby protecting the operating system, task code, and data from
errant tasks. Address translation enables implementation of a software model in which the code
uses virtual addresses that are translated to physical addresses accessing memory. The MMU
provides a virtual memory software model with a hole for the OCE and internal device registers
and peripherals. The core generates virtual addresses during its operation. The virtual address
together with the task ID from the MMU become the task-extended (TE) virtual address. The
MMU translates between virtual and physical addresses during each core access, providing
control attributes for each core access per memory segment, such as burst size, pre-fetch enable,
write-policy, cacheability, and so forth.
The MMU has the following functions and features:
A memory attributes and translation table (MATT), composed of 20 data segment
descriptors and 12 program segment descriptors.
Each segment descriptor defines a related memory region and its cache and attributes,
protection and address translation.
The descriptor related memory space has a long-range variable mapping size. The size is
designated in steps as a power of 2, starting from 256 bytes. The mapping size can be
between 256 bytes to 4 GB. The base address must be aligned to a segment size.
The memory region dedicated cache and attributes support the following:
— Cacheable access.
— A burst size of 1 or 4 for the data fetch unit (DFU) and instruction fetch unit (IFU).
— Pre-fetch line enable.
— System/shared attributes
— Global attributes
— Write policy for data memory
— L2 cache policy data memory
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...