AN2692

Embedded application aspects

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3

Embedded application aspects

This section advises for embedded applications where the ST10F269Zx embedded Flash

memory may be the only non-volatile memory available.

Reading the Flash memory while programming and field reprogramming are the two specific

points raised by single-chip embedded applications.

3.1

Reading the Flash memory while erasing or programming

During erasing or programming, the entire Flash memory is not visible to the CPU, whatever

the Flash memory block being erased or programmed. As a consequence on ST10F269Zx

software:

●

During erasing and programming, it is not possible to have access to the interrupt

vector table and so all interrupts shall be disabled.

●

Before erasing and programming, a small software loop shall be copied from the Flash

memory to the on-chip RAM to run the minimum code needed to wait for the end of

erasing or programming.

●

If code protection is activated, it should be temporarily disabled before executing the

code copied into the on-chip RAM.

There are two ways of dealing with this constraint: one consists in minimizing the

requirements in RAM space during erasing/programming, and the other consists in

maximizing the programming speed by duplicating all needed software into the on-chip

RAM.

3.1.1

Minimum software to be copied into the on-chip RAM

The minimum software to be copied into the on-chip RAM is:

●

Functions sending the erasing and/or programming commands to the ST10F269Zx

embedded Flash memory,

●

Functions polling the Flash memory Status Register for completion of the command

and for error (see detailed specification).

Example of use: This method can be implemented when it is necessary to program and/or

erase some data in the ST10F269Zx embedded Flash memory during normal operation.

3.1.2

Maximizing programming performance at system level

When the minimum software is copied into the on-chip RAM, during erasing and/or

programming, the CPU cannot run any other software (like communication).

To maximize the programming performance, the user could handle the whole part or only

part of the communication handler. This requires:

●

That more software is copied into the on-chip RAM,

●

The communication handler is not using interrupts,

●

The software loop polling the Flash memory Status Register is modified to handle the

Communication process.

Example of use: This method can be implemented when it is necessary to erase and

program (reprogram) the whole ST10F269Zx Flash memory.