C8051F38B-GMR View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F38B-GMR

Full Speed USB Flash MCU Family

Silicon Laboratories 

C8051F380/1/2/3/4/5/6/7/C

18.2. 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.

18.3. 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 soft-

ware 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 also locked when any other Flash pages are locked. See exam-

ple below.

Security Lock Byte:

1s Complement:

Flash pages locked:

Addresses locked:

11111101b

00000010b

3 (2 + Flash Lock Byte Page)

First two pages of Flash: 0x0000 to 0x03FF

Flash Lock Byte Page: (0xFA00 to 0xFBFF for 64k devices; 0x7E00 to

0x7FFF for 32k devices, 0x3E00 to 0x3FFF for 16k devices)

FLASH memory

organized in 512-byte

pages

C8051F380/2/4/6

Reserved

Lock Byte

0xFC00

0xFBFF

0xFBFE

0xFA00

Unlocked FLASH Pages

Locked when any

other FLASH pages

are locked

C8051F381/3/5/7

Lock Byte

Unlocked FLASH Pages

0x7FFF

0x7FFE

0x7E00

C8051F38C

Lock Byte

Unlocked FLASH Pages

0x3FFF

0x3FFE

0x3E00

0x0000

0x0000

0x0000

Access limit set

according to the

FLASH security lock

byte

Figure 18.1. Flash Program Memory Map and Security Byte

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.

Rev. 1.4

137

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