SAM3N4A Atmel Corporation, SAM3N4A Datasheet - Page 62
SAM3N4A
Manufacturer Part Number
SAM3N4A
Description
Manufacturer
Atmel Corporation
Specifications of SAM3N4A
Flash (kbytes)
256 Kbytes
Pin Count
48
Max. Operating Frequency
48 MHz
Cpu
Cortex-M3
# Of Touch Channels
32
Hardware Qtouch Acquisition
No
Max I/o Pins
79
Ext Interrupts
79
Quadrature Decoder Channels
2
Usb Speed
No
Usb Interface
No
Spi
2
Twi (i2c)
2
Uart
3
Ssc
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
8
Adc Resolution (bits)
10
Adc Speed (ksps)
384
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
24
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8/3.3
Operating Voltage (vcc)
1.62 to 3.6
Fpu
No
Mpu / Mmu
no / no
Timers
6
Output Compare Channels
6
Input Capture Channels
3
Pwm Channels
4
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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SAM3N
Software must use a Load-Exclusive instruction with the corresponding Store-Exclusive
instruction.
To perform a guaranteed read-modify-write of a memory location, software must:
Software can use the synchronization primitives to implement a semaphores as follows:
The Cortex-M3 includes an exclusive access monitor, that tags the fact that the processor has
executed a Load-Exclusive instruction. If the processor is part of a multiprocessor system, the
system also globally tags the memory locations addressed by exclusive accesses by each
processor.
The processor removes its exclusive access tag if:
In a multiprocessor implementation:
For more information about the synchronization primitive instructions, see
on page 100
• the halfword instructions LDREXH and STREXH
• the byte instructions LDREXB and STREXB.
• Use a Load-Exclusive instruction to read the value of the location.
• Update the value, as required.
• Use a Store-Exclusive instruction to attempt to write the new value back to the memory
• Use a Load-Exclusive instruction to read from the semaphore address to check whether the
• If the semaphore is free, use a Store-Exclusive to write the claim value to the semaphore
• If the returned status bit from the second step indicates that the Store-Exclusive succeeded
• It executes a CLREX instruction
• It executes a Store-Exclusive instruction, regardless of whether the write succeeds.
• An exception occurs. This means the processor can resolve semaphore conflicts between
• executing a CLREX instruction removes only the local exclusive access tag for the processor
• executing a Store-Exclusive instruction, or an exception. removes the local exclusive access
location, and tests the returned status bit. If this bit is:
semaphore is free.
address.
then the software has claimed the semaphore. However, if the Store-Exclusive failed, another
process might have claimed the semaphore after the software performed the first step.
different threads.
tags, and all global exclusive access tags for the processor.
0: The read-modify-write completed successfully,
1: No write was performed. This indicates that the value returned the first step might be out
of date. The software must retry the read-modify-write sequence,
and
“CLREX” on page
102.
“LDREX and STREX”
11011A–ATARM–04-Oct-10
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