RM0312 datasheet(27/275 Pages) STMICROELECTRONICS

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RM0312

Flash program memory and data EEPROM

4.4.1

Proprietary code area (PCODE)

The proprietary code area (PCODE) can be used to protect proprietary software libraries

used to drive peripherals.

The size of the PCODE area can be configured through the PCODE option byte

(PCODESIZE) in ICP mode (using the SWIM interface). This option byte specifies the

number of pages (64-byte granularity) allocated for the PCODE area starting from address

0x00 8000. Once programmed, the PCODE option byte cannot be erased, and the size of

the PCODE area remains fixed.

The minimum meaningful size of the PCODE area is 1 page ranging from address 0x8080

to 0x80BF while the PCODESIZE is set to the value 3. The maximum size of the PCODE

area is 253 pages ranging from address 0x00 8080 to 0x00 BFBF (while the PCODESIZE is

0xFF). In this case, only one page is left either for the main program area or for data

EEPROM. While the PCODE is enabled the TRAP interrupt vector is write protected.

The PCODE area is automatically readout protected except for the TRAP interrupt vector

(see Section 4.5.1: Readout protection). The readout protection cannot be disabled in this

area. This means that the content of the PCODE area cannot be read or modified.

The PCODE area can be accessed only through the TRAP vector.

4.4.2

User boot area (UBC)

The user boot area (UBC) contains the reset and the interrupt vectors. It can be used to

store the IAP and communication routines. The UBC area has a second level of protection

to prevent unintentional erasing or modification during IAP programming. This means that it

is always write protected and the write protection cannot be unlocked using the MASS keys.

The size of the UBC area can be obtained by reading the UBC option byte.

The size of the UBC area can be configured in ICP mode (using the SWIM interface)

through the UBC option byte. The UBC option byte specifies the number of pages allocated

for the UBC area starting from address 0x00 8000.

The minimum meaningful size of the UBC area is of 3 pages of which 2 are used to store the

interrupt vectors.

Note:

When a PCODE area has been defined, the minimum size of the UBC should be

PCODESIZE+1. The portion of the UBC available to store the boot code is the area located

between the end of the PCODE area and the end of the defined UBC area.

The maximum size of the boot area is 255 pages ranging from address 0x00 8000 to

0x00 BFBF (including the interrupt vectors). In this case, only one page is left either for the

main program area or for data EEPROM.

Refer to Figure 5 for a description of the UBC area memory mapping and to the option byte

section in the datasheets for more details on the UBC option byte.

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