SAM9XE512 Atmel Corporation, SAM9XE512 Datasheet - Page 59

• Manufacturer Part Number: SAM9XE512
• Manufacturer: Atmel Corporation

Specifications of SAM9XE512

• Flash (kbytes): 512 Kbytes
• Pin Count: 217
• Max. Operating Frequency: 180 MHz
• Cpu: ARM926
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 96
• Ext Interrupts: 96
• Usb Transceiver: 3
• Usb Speed: Full Speed
• Usb Interface: Host, Device
• Spi: 2
• Twi (i2c): 2
• Uart: 6
• Ssc: 1
• Ethernet: 1
• Sd / Emmc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: Yes
• Adc Channels: 4
• Adc Resolution (bits): 10
• Adc Speed (ksps): 312
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 32
• Self Program Memory: NO
• External Bus Interface: 1
• Dram Memory: sdram
• Nand Interface: Yes
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8/3.3
• Operating Voltage (vcc): 1.65 to 1.95
• Fpu: No
• Mpu / Mmu: No / Yes
• Timers: 6
• Output Compare Channels: 6
• Input Capture Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: No

11.6.2.2
11.6.2.3
11.6.2.4
6254C–ATARM–22-Jan-10
Write Buffer
Write-though Operation
Write-back Operation
cache line is replaced due to a linefill or a cache clean operation, the dirty bits are used to decide
whether all, half or none is written back to memory.
DCache can be enabled or disabled by writing either 1 or 0 to bit C in register 1 of CP15 (see
Tables 4-3 and 4-4 on page 4-5 in ARM926EJ-S TRM).
The DCache supports write-through and write-back cache operations, selected by memory
region using the C and B bits in the MMU translation tables.
The DCache contains an eight data word entry, single address entry write-back buffer used to
hold write-back data for cache line eviction or cleaning of dirty cache lines.
The Write Buffer can hold up to 16 words of data and four separate addresses. DCache and
Write Buffer operations are closely connected as their configuration is set in each section by the
page descriptor in the MMU translation table.
The ARM926EJ-S contains a write buffer that has a 16-word data buffer and a four- address buf-
fer. The write buffer is used for all writes to a bufferable region, write-through region and write-
back region. It also allows to avoid stalling the processor when writes to external memory are
performed. When a store occurs, data is written to the write buffer at core speed (high speed).
The write buffer then completes the store to external memory at bus speed (typically slower than
the core speed). During this time, the ARM9EJ-S processor can preform other tasks.
DCache and Write Buffer support write-back and write-through memory regions, controlled by C
and B bits in each section and page descriptor within the MMU translation tables.
When a cache write hit occurs, the DCache line is updated. The updated data is then written to
the write buffer which transfers it to external memory.
When a cache write miss occurs, a line, chosen by round robin or another algorithm, is stored in
the write buffer which transfers it to external memory.
When a cache write hit occurs, the cache line or half line is marked as dirty, meaning that its
contents are not up-to-date with those in the external memory.
When a cache write miss occurs, a line, chosen by round robin or another algorithm, is stored in
the write buffer which transfers it to external memory.
AT91SAM9XE128/256/512 Preliminary
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