C8051F352 Datasheet, PDF (123/234 Pages) Silicon Laboratories – 8 k ISP Flash MCU Family

C8051F350/1/2/3
15.2. Non-volatile Data Storage
The Flash memory can be used for non-volatile data storage as well as program code. This allows data
such as calibration coefficients to be calculated and stored at run time. Data is written using the MOVX
write instruction and read using the MOVC instruction. Note: MOVX read instructions always target XRAM.
15.3. 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 locked when any other Flash pages are locked. See exam-
ple below.
Security Lock Byte:
1’s Complement:
Flash pages locked:
Addresses locked:
11111101b
00000010b
3 (First two Flash pages + Lock Byte Page)
0x0000 to 0x03FF (first two Flash pages) and
0x1C00 to 0x1DFF (Lock Byte Page)
Locked when any
other Flash pages are
locked
Access limit set
according to the Flash
security lock byte
Reserved
Lock Byte
0x1E00
0x1DFF
0x1DFE
0x1C00
Unlocked Flash Pages
Flash memory organized
in 512-byte pages
0x0000
Figure 15.1. Flash Memory Map
Rev. 1.1
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