How do I Atomic Operation control the non-bit banding region in STM32F4 and STM32F1 ?

But I'm wondering how do I control non-BitBand Alias part in memory map.

You don't control anything of bit-banding, this is a built in and fixed option.

Bit-banding works in the following way: on the output of processor (its S-port to be precise), where it attaches to the bus matrix, there is a small insert with an address comparator for the 22000000-23ffffff and 42000000-43ffffff addresses.

Whenever the processor tries to read from one of those areas, this insert intercepts the read, transforms the address to the non-bit-band version, performs the read but retains the result, extracts the given bit according to the original address to produce 0x00000000 or 0x00000001 and submits it to the processor.

Whenever the processor tries to write to one of those areas, this insert intercepts the write, transforms the address to the non-bit-band version, performs a read from that address while locking down the target bus (i.e. no other master (such as DMA) can access the bus), in the read data replaces the bit given by original address by the lowest bit from data written by processor, and writes back the result to the non-bit-band version of address, while unlocking the bus.

Note, that this is present only in Cortex-M3 and M4, *not* in M0/M0+ and *not even* in M7, so if you intend to migrate upwards or downwards, better don't use it. Note also, that this insert is a configuration option, and while all STM32 M3/M4 contain it, some other vendors chose not to use it (e.g. some of the ATSAMs), so if you intend to migrate across mcu vendors, better don't use it.

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http://www.efton.sk/STM32/bitbandcalc.html

JW

If you need to do atomic operations (not necessarily limited to bit-band ones) on non-bit-band memory, you are forced to use 'other means' to achieve the atomicity.

For example you could disable all interrupts*, do the operation and then restore interrupts. That's what I had to do when porting bit-band code to stm32f7. The details will vary depending on your environment (e.g. if you're using a real-time operating-system, and if so which). This code uses Rowley's Crossworks Tasking Library:

/* stm32f7 does not have bit-banding */

#define DISABLE_INTERRUPTS  int en = ctl_global_interrupts_disable()

#define ENABLE_INTERRUPTS   if (en) ctl_global_interrupts_enable()

void peripheral_bitband_write(volatile unsigned *address, int bit, unsigned int value)

{

     DISABLE_INTERRUPTS;

     *address = (*address & ~(1 << bit)) | (value ? 1 << bit : 0);

     ENABLE_INTERRUPTS;

}

*This isn't sufficient if DMA activity could modify the memory word.

Hope this helps,

Danish