HD6417720BP133BV Renesas Electronics America, HD6417720BP133BV Datasheet - Page 226

• Manufacturer Part Number: HD6417720BP133BV
• Description: SH3-DSP, WITH USB AND LCDC, PB-F
• Manufacturer: Renesas Electronics America
• Series: SuperH® SH7700r

Specifications of HD6417720BP133BV

• Core Processor: SH-3 DSP
• Core Size: 32-Bit
• Speed: 133MHz
• Connectivity: FIFO, I²C, IrDA, MMC, SCI, SD, SIO, SIM, USB
• Peripherals: DMA, LCD, POR, WDT
• Number Of I /o: 117
• Program Memory Type: ROMless
• Ram Size: 16K x 8
• Voltage - Supply (vcc/vdd): 1.4 V ~ 1.6 V
• Data Converters: A/D 4x10b; D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 75°C
• Package / Case: 256-BGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

Section 4 Memory Management Unit (MMU)
Although the functions of the MMU could also be implemented by software alone, the need for
translation to be performed by software each time a process accesses physical memory would
result in poor efficiency. For this reason, a buffer for address translation (translation look-aside
buffer: TLB) is provided in hardware to hold frequently used address translation information. The
TLB can be described as a cache for storing address translation information. Unlike cache
memory, however, if address translation fails, that is, if an exception is generated, switching of
address translation information is normally performed by software. This makes it possible for
memory management to be performed flexibly by software.
The MMU has two methods of mapping from virtual memory to physical memory: a paging
method using fixed-length address translation, and a segment method using variable-length
address translation. With the paging method, the unit of translation is a fixed-size address space
(usually of 1 to 64 kbytes) called a page.
In the following text, the address space in virtual memory is referred to as virtual address space,
and address space in physical memory as physical memory space.
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Process 1
Physical
memory
Process 1
Process 1
Process 2
Process 3
Figure 4.1 MMU Functions
Physical
memory
Physical
memory
(3)
(1)
Process 1
Process 2
Process 3
Process 1
memory
memory
Virtual
Virtual
SH7720 Group, SH7721 Group
R01UH0083EJ0400 Rev. 4.00
MMU
MMU
Physical
memory
Physical
memory
Sep 21, 2010
(4)
(2)