ST10F271 datasheet(28/173 Pages) STMICROELECTRONICS

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Internal Flash memory

ST10F271

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During a Write operation, when bit LOCK of FCR0 is set, it is forbidden to write into the

Flash Control Registers.

Power supply drop

If during a write operation the internal low voltage supply drops below a certain internal

voltage threshold, any write operation running is suddenly interrupted and the module is

reset to Read mode. At following Power-on, the interrupted Flash write operation must be

repeated.

5.4

Registers description

5.4.1

Flash control register 0 low

The Flash Control Register 0 Low (FCR0L) together with the Flash Control Register 0 High

(FCR0H) is used to enable and to monitor all the write operations on the IFLASH. The user

has no access in write mode to the Test-Flash (B0TF). Besides, Test-Flash block is seen by

the user in Bootstrap Mode only.

5.4.2

Flash control register 0 high

The Flash Control Register 0 High (FCR0H) together with the Flash Control Register 0 Low

(FCR0L) is used to enable and to monitor all the write operations on the IFLASH. The user

FCR0L (0x08 0000)

FCR

Reset Value: 0000h:

987

65432

reserved

LOCK

res.

BSY0

res.

Table 7.

Flash control register 0 low

Bit

Function

BSY0

Bank 0 Busy (IFLASH)

This bit indicates that a write operation is running on Bank 0 (IFLASH). It is

automatically set when bit WMS is set. Setting Protection operation sets bit BSY0

(since protection registers are in this Block). When this bit is set, every read

access to Bank 0 will output invalid data (software trap 009Bh), while every write

access to the Bank will be ignored. At the end of the write operation or during a

Program or Erase Suspend this bit is automatically reset and the Bank returns to

read mode. After a Program or Erase Resume this bit is automatically set again.

LOCK

Flash Registers Access Locked

When this bit is set, it means that the access to the Flash Control Registers

FCR0H/-FCR1H/L, FDR0H/L-FDR1H/L, FARH/L and FER is locked by the FPEC:

any read access to the registers will output invalid data (software trap 009Bh) and

any write access will be ineffective. LOCK bit is automatically set when the Flash

bit WMS is set.

This is the only bit the user can always access to detect the status of the Flash:

once it is found low, the rest of FCR0L and all the other Flash registers are

accessible by the user as well.

Note that FER content can be read when LOCK is low, but its content is updated

only when also BSY0 bit is reset.

ST10F271 Datasheet(PDF) 28 Page - STMicroelectronics

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