HD6417727F160V Renesas Electronics America, HD6417727F160V Datasheet - Page 156

• Manufacturer Part Number: HD6417727F160V
• Description: MPU 3V 16K PB-FREE 240-QFP
• Manufacturer: Renesas Electronics America
• Series: SuperH® SH7700r

Specifications of HD6417727F160V

• Core Processor: SH-3 DSP
• Core Size: 32-Bit
• Speed: 160MHz
• Connectivity: FIFO, SCI, SIO, SmartCard, USB
• Peripherals: DMA, LCD, POR, WDT
• Number Of I /o: 104
• Program Memory Type: ROMless
• Ram Size: 32K x 8
• Voltage - Supply (vcc/vdd): 1.7 V ~ 2.05 V
• Data Converters: A/D 6x10b; D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 75°C
• Package / Case: 240-QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

Section 3 Memory Management Unit (MMU)
When address translation from virtual memory to physical memory is performed using the MMU,
it may occur that the relevant translation information is not recorded in the MMU, with the result
that one process may inadvertently access the virtual memory allocated to another process. In this
case, the MMU will generate an exception, change the physical memory mapping, and record the
new address translation information.
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 SH7727 address space in virtual memory is referred to as logical address
space, and address space in physical memory as physical memory space.
Rev.6.00 Mar. 27, 2009 Page 98 of 1036
REJ09B0254-0600