C8051F310 datasheet(113/228 Pages) SILABS

113 / 228 page

Rev. 1.7

113

C8051F310/1/2/3/4/5/6/7

10.3. Security Options

The CIP-51 provides security options to protect the Flash memory from inadvertent modification by soft-

ware as well as to prevent the viewing of proprietary program code and constants. The Program Store

Write Enable (bit PSWE in register PSCTL) and the Program Store Erase Enable (bit PSEE in register

PSCTL) bits protect the Flash memory from accidental modification by software. PSWE must be explicitly

set to ‘1’ before software can modify the Flash memory; both PSWE and PSEE must be set to ‘1’ before

software can erase Flash memory. Additional security features prevent proprietary program code and data

constants from being read or altered across the C2 interface.

A Security Lock Byte located at the last byte of Flash user space offers protection of the Flash program

memory from access (reads, writes, or erases) by unprotected code or the C2 interface. The Flash security

mechanism allows the user to lock n 512-byte Flash pages, starting at page 0 (addresses 0x0000 to

0x01FF), where n is the 1’s complement number represented by the Security Lock Byte. Note that the

page containing the Flash Security Lock Byte is unlocked when no other Flash pages are locked

(all bits of the Lock Byte are ‘1’) and locked when any other Flash pages are locked (any bit of the

Lock Byte is ‘0’). See the example below.

Figure 10.1. Flash Program Memory Map

Security Lock Byte:

11111101b

1’s Complement:

00000010b

Flash pages locked:

3 (First two Flash pages + Lock Byte Page)

Addresses locked:

0x0000 to 0x03FF (first two Flash pages)

and 0x3C00 to 0x3DFF or 0x1E00 to 0x1FFF (Lock Byte Page)

Access limit set

according to the

FLASH security lock

byte

C8051F310/1/6/7

0x0000

0x3DFF

Lock Byte

Reserved

0x3DFE

0x3E00

FLASH memory

organized in 512-byte

pages

0x3C00

Unlocked FLASH Pages

Locked when any

other FLASH pages

are locked

C8051F312/3/4/5

0x0000

0x1FFF

Lock Byte

Reserved

0x1FFE

0x2000

0x1E00

Unlocked FLASH Pages

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