# CARD_WriteFlashAsync

## Syntax

  `#include <nitro/card.h>`
  `static inline void CARD_WriteFlashAsync( u32 dst, const void *src, u32 len, MIDmaCallback callback, void *arg);`

## Arguments

dst | The FLASH address of the transfer destination.
src | Transfer source memory address.
len | Byte length of data to be written.
callback | Completion callback function. Specify `NULL` if this is unnecessary. This callback is called from within the interrupt handler.
arg | Arguments to pass to the completion callback function. This is simply ignored if `NULL` was specified for `callback`.

## Return Values

None.

## Description

Writes data asynchronously to a flash device. This function immediately returns control. Use the `CARD_WaitBackupAsync` function to wait for processing to end. To determine the processing result, call the `CARD_GetResultCode` function after processing has ended.

## Note

- To use this function, you must first lock the access bus with the `CARD_LockBackup` function.
- This function communicates with the ARM7 processor internally via PXI. The process will not end if PXI interrupts are not enabled.
- The function uses an internal thread to execute an asynchronous process. See the description of the `CARD_GetThreadPriority` function for more information on this thread.
- Because some high-capacity flash devices do not support "Write" operations, CARD_RESULT_UNSUPPORTED is returned and execution fails even if this function is called. See the Backup Access Overview for more details, and then use substitute functions, such as `CARD_WriteFlashSector`, when necessary.

## See Also

`CARD_IsBackupFlash, CARD_WaitBackupAsync, CARD_GetResultCode, CARD_ReadFlash, CARD_WriteFlash, CARD_VerifyFlash, CARD_WriteAndVerifyFlash, CARD_GetThreadPriority`

## Revision History

2007/11/13 Added a note regarding the fact that some high-capacity flash devices cannot use this function.
2005/06/01 Added a statement indicating that callback is called from interrupt handler.
2004/12/09 Changed "IO processor" to "ARM7 processor".
2004/11/02 Revised links.
2004/08/23 Initial version.

CONFIDENTIAL