ST10F272M datasheet(28/175 Pages) STMICROELECTRONICS

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Internal Flash memory

ST10F272M

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5.3

Write operation

The Flash module has one single register interface mapped in the memory space of the

IBus (08’0000h - 08’0015h). All the operations are enabled through four 16-bit control

registers: Flash Control Register 1-0 High/Low (FCR1H/L-FCR0H/L). Eight other 16-bit

registers are used to store Flash address and data for program operations (FARH/L and

FDR1H/L-FDR0H/L) and Write Operation Error flags (FERH/L). All registers are accessible

with 8- and 16-bit instructions (since the IBUS operates in 16-bit mode for read/write

accesses to data).

Note:

The register that controls the Temporary Unprotection of the Flash is located on the XBus at

address 00’EB50h in the XMiscellaneous Register area.

Before accessing the IFlash module (and consequently the Flash register to be used for

program/erasing operations), the ROMEN bit in SYSCON register must be set.

Caution:

During a Flash write operation any attempt to read the Flash itself, that is under

modification, will output invalid data (software trap 009Bh). This means that the Flash is not

fetchable when a programming operation is active:The write operation commands must

be executed from another memory (internal RAM or external memory), as in ST10F269

device. In fact, due to IBus characteristics, it is not possible to perform a write operation on

IFlash, when fetching code from IFlash.

Direct addressing is not allowed for write accesses to IFlash Control Registers.

Warning:

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 (FCR0L)

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

(FCR0H) are 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). Moreover, the Test-Flash block is

seen by the user in Bootstrap mode only.

FCR0L (0x08 0000)

FCR

Reset value: 0000h

987

65432

Reserved

LOCK Reserved BSY0 Res.

-RO

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