SAM3U2E Atmel Corporation, SAM3U2E Datasheet - Page 76

• Manufacturer Part Number: SAM3U2E
• Manufacturer: Atmel Corporation

Specifications of SAM3U2E

• Flash (kbytes): 128 Kbytes
• Pin Count: 144
• Max. Operating Frequency: 96 MHz
• Cpu: Cortex-M3
• # Of Touch Channels: 57
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 96
• Ext Interrupts: 96
• Usb Transceiver: 1
• Quadrature Decoder Channels: 1
• Usb Speed: Hi-Speed
• Usb Interface: Device
• Spi: 5
• Twi (i2c): 2
• Uart: 5
• Ssc: 1
• Sd / Emmc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 12
• Adc Speed (ksps): 384
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 36
• Self Program Memory: YES
• External Bus Interface: 1
• Dram Memory: No
• Nand Interface: Yes
• 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: Yes / No
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 3
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

13.4.8
76
SAM3U Series
Programming hints for the synchronization primitives
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 114
ANSI C cannot directly generate the exclusive access instructions. Some C compilers provide
intrinsic functions for generation of these instructions:
Table 13-8.
The actual exclusive access instruction generated depends on the data type of the pointer
passed to the intrinsic function. For example, the following C code generates the require
LDREXB operation:
Instruction
LDREX, LDREXH, or
LDREXB
STREX, STREXH, or
STREXB
CLREX
• 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
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.
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,
__ldrex((volatile char *) 0xFF);
and
C compiler intrinsic functions for exclusive access instructions
“CLREX” on page
Intrinsic function
unsigned int __ldrex(volatile void *ptr)
int __strex(unsigned int val, volatile void *ptr)
void __clrex(void)
116.
“LDREX and STREX”
6430E–ATARM–29-Aug-11