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XFLASH DRIVER

1.1.3 User functions

The XFlash driver allows user specific functions to be executed while an XFlashWriteBlock

function is executing. Writing 256 bytes requires several tenths of a millisecond during which

time you may have to manage some tasks: A typical example is to refresh the watchdog, in

order to avoid a Reset during XFlash reprogramming.

For this purpose the driver provides 1 function named UserWhileWriteBlock that you have to

define in your firmware (take care to not use the RAM area with the driver variables).

Finally, the Interrupts are reenabled (RIM assembler instruction) by the driver before the exe-

cution of the UserWhileWrite function.

1.2 DRIVER ARCHITECTURE

1.2.1 Driver principle

When called by the user firmware in Flash Sector 0, the XflashWriteBlock executes the fol-

lowing sequence:

– Load the RAM Page 0 with a programming algorithm

– Execute this programming algorithm from RAM

– Return to the user firmware in Flash Sector 0, just after the XflashWriteBlock instruction.

At this point the RAM area used by the programming algorithm is released and is available to

the user firmware.

1.2.2 Memory management

The programming algorithm requires 20 bytes and is positioned at the end of RAM Page 0.

In addition, 7 bytes in RAM Page 0 are reserved for the IAP driver internal variables.

The location of the 27 bytes (algorithm plus variables) is defined in the Xflash.h file by the pa-

rameter STACK_END: The location is then 0xE4h-0xFFh for a ST72F264 MCU.

It is important to note these 27 bytes are used only during the XFlashWriteBlock execution:

You can still use this area in his application firmware (except in the UserWhileWriteBlock func-

tion) as long as he accepts they are overwritten during the IAP process.