ST10F272B_12 STMICROELECTRONICS [STMicroelectronics], ST10F272B_12 Datasheet - Page 31

• Manufacturer Part Number: ST10F272B_12
• Description: 16-bit MCU with 256 Kbyte Flash memory and 12/20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST10F272B/ST10F272E
5.3
Write operation
The Flash module have one single register interface mapped in the memory space of the
IBUS (0x08 0000 to 0x08 0015). 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 operates in 16-bit mode when in read/ write).
Before accessing the IFlash module (and consequently also the Flash register to be used for
program/erasing operations), bit ROMEN in SYSCON register shall be set.
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.
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.
Doc ID 11917 Rev 3
Internal Flash memory
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