Embedded application aspects

AN2692

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3.1.3

Erase Suspend and Resume commands

Like in standalone Flash memories, the 0.35 µm embedded Flash memory controller

features suspend and resume commands. These commands are used to suspend the

erasing or programming process at any time, and resume it later on.

Once the suspend command is complete, the ST10F269Zx can access a needed software

routine (the communication driver) which has not been relocated in the on-chip RAM.

Example of use: the error handler of the communication driver.

Note:

The time during which the Flash memory is not available is unchanged but this gives the

possibility of suspending the process to run specific routines during Flash memory erasing

or programming (e.g.: communication protocol).

3.2

Field reprogramming with ST10F269Zx

Reprogramming in the field part or the whole application requires to be able to deal safely

with all the events that may occur in the field while the Flash memory is being

reprogrammed.

This analysis is application-dependent and has to be carefully conducted by the user. This

section assumes that users are experienced with all the generic aspects of field

reprogramming and will focus only on the ST10F269Zx specific events.

3.2.1

Field events and Flash memory reliability

The user applications must meet ST’s recommendations for Flash memory programming

and erasing. Failure to do so could result in lower data retention and/or altered Flash

memory reliability. The conditions leading to an altered data retention or to an altered

reliability depend on the command issued to the Flash memory and the event that occurred

during this command (supply out of range, reset).

From the FMEA (failure modes and effects analysis) perspective, customers should

consider that when ST’s advice is not implemented, the Flash memory reliability can be

altered. When ST’s advice is implemented, and provided that all field-specific events are

within ST recommendations (see hereafter), the Flash memory will meet ST’s published

specification.

3.2.2

Reset

Whatever the possible causes of reset (spurious reset, external hardware reset, reset due to

power shutdown), Reset is one of the events that may happen during field reprogramming.

Reset and boot block

Reset may occur at any time and there is no way of preventing this. Reset may occur during

the reprogramming of the boot block (block 0) and thus leave invalid data/code inside this

block.

Suggested method of handling: as reset may occur during the erasing of the on-chip Flash

memory before it is reprogrammed, the ST10F269Zx should be able to read a valid code

from the Flash memory at the next startup.