ATSAM3S1BA-AU Atmel, ATSAM3S1BA-AU Datasheet - Page 62

• Manufacturer Part Number: ATSAM3S1BA-AU
• Description: IC MCU 32BIT 64KB FLASH 64LQFP
• Manufacturer: Atmel
• Series: SAM3Sr

Specifications of ATSAM3S1BA-AU

• Core Processor: ARM® Cortex-M3™
• Core Size: 32-Bit
• Speed: 64MHz
• Connectivity: I²C, MMC, SPI, SSC, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, DMA, I²S, POR, PWM, WDT
• Number Of I /o: 47
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Ram Size: 16K x 8
• Voltage - Supply (vcc/vdd): 1.62 V ~ 1.95 V
• Data Converters: A/D 10x10/12b, D/A 2x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-LQFP
• Controller Family/series: ATSAM3S
• No. Of I/o's: 47
• Ram Memory Size: 16KB
• Cpu Speed: 64MHz
• No. Of Timers: 6
• Rohs Compliant: Yes
• Processor Series: ATSAM3x
• Core: ARM Cortex M3
• 3rd Party Development Tools: JTRACE-CM3, MDK-ARM, RL-ARM, ULINK2
• Development Tools By Supplier: ATSAM3S-EK
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

10.5.8
62
SAM3S Preliminary
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 100
ANSI C cannot directly generate the exclusive access instructions. Some C compilers provide
intrinsic functions for generation of these instructions:
Table 10-8.
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)
102.
“LDREX and STREX”
6500C–ATARM–8-Feb-11