C8051F91X-C8051F90X 데이터 시트보기 (PDF) - Silicon Laboratories

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C8051F91X-C8051F90X

Single/Dual Battery, 0.9–3.6 V, 16–8 kB, SmaRTClock, 12/10-Bit ADC MCU

Silicon Laboratories 

C8051F91x-C8051F90x

13.3. Security Options

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

software 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 1s 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).

Security Lock Byte:

ones Complement:

Flash pages locked:

1111 1011b

0000 0100b

5 (First four Flash pages + Lock Byte Page)

Addresses locked:

0x0000 to 0x07FF (first four Flash pages) and

0x3A00 to 0x3BFF (Lock Byte Page)

16KB Flash Device

(SFLE = 0)

8KB Flash Device

(SFLE = 0)

0xFFFF

0x3C00

0x3BFF

0x3BFE

0x3A00

Reserved

Lock Byte

Lock Byte Page

Unlocked Flash Pages

0x0000

Locked when

any other

Flash pages

are locked

Access limit

set according

to the Flash

security lock

byte

0xFFFF

Reserved

Lock Byte

Lock Byte Page

0x2000

0x1FFF

0x1FFE

0x1E00

Unlocked Flash Pages

0x0000

16/8 KB Flash Device

(SFLE = 1)

Scratchpad Area

(Data Only)

0x01FF

0x0000

Figure 13.1. Flash Program Memory Map (16 kB and 8 kB devices)

Flash

memory

organized in

512-byte

pages

The level of Flash security depends on the Flash access method. The three Flash access methods that

can be restricted are reads, writes, and erases from the C2 debug interface, user firmware executing on

unlocked pages, and user firmware executing on locked pages. Table 13.1 summarizes the Flash security

features of the C8051F91x-C8051F90x devices.

134

Rev. 1.0

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