Emif Global Reset Register; Dsp Memory Management Unit; Description - Texas Instruments OMAP5912 Reference Manual

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Table 17. EMIF Global Control Register (EMIF GCR) (Continued)

EMIF Global Reset Register

DSP Memory Management Unit

DSP Subsystem

Any write in the EMIF global reset register (EMIF_GRR) register causes a

software reset of the EMIF state machines. This register cannot be read. A

software reset does not change the current configuration register values

(EMIF_GCR, and so on); only the EMIF state machines are reset. The EMIF

GRR appears at word address 0x0801 in the DSP I/O space.

The DSP MMU maps the 16M bytes of the DSP virtual external addresses to

anyplace in the 4G-byte address space of the OMAP5912 device. At reset the

MMU is disabled and the DSP external memory space is mapped to the first

16M bytes of CS0 system memory.

The DSP MMU translates the 24-bit DSP external addresses (028000 to

FF8000 or FFFF00) to physical addresses in the 32-bit MPU address space.

Address translation is performed by a translation table structure (TTB) that

maps the most significant bits of the DSP byte address onto another set of

most significant bits of a 32-bit MCU byte address. The least significant bits

of the DSP-generated byte address are not altered when forming the new

address. The TTB translations are expedited by a cache-like translation

look-aside buffer mechanism (TLB). The address mapping can be

programmed at the TTB level or by writing the TLB entries directly. The DSP

MMU contains 32 TLB entries that can be configured to remap 1M-byte,

64K-byte, 4K-byte, or 1K-byte segments of memory.

The DSP MMU is programmed by the ARM926EJS. In general, the MMU is

initialized at boot time, but it also can be reprogrammed dynamically. The MMU

is programmed through the TIPB registers. DSP MMU registers have an MPU

base address of 0xFFFE:D200.

The DSP MMU is in the TC clock frequency domain (i.e. runs as fast as the

TC_CK). The DSP memory management unit (MMU) supports memory

mapping for the DSP. The platform system software can relocate regions of the

DSP logical address space via a page table and the DSP MMU.

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