PC87591L datasheet(435/437 Pages) NSC

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B.2

PROTECTION INFORMATION

The flash protection word is used to protect the contents of the on-chip flash from being altered. It also prevents the system

from executing from an erased flash and sets various system defaults. The following are examples of common settings for the

protection word. The protection word should be written into the flash as the last operation after updating the flash via the JTAG.

The protection word may be written by a write operation, using the programing tool to address 00FE16 in the information block

(block 2). Note that the protection word must be updated in all operating environments (DEV, OBD, PROG and IRE).

Example 1

Core boot block size is 4 Kbytes

— Bit 3-0 (Core Boot Block): 1110

●

Shared BIOS using an expansion memory

— Bit 4 (Host Boot Block): 1

— Bit 6 (Force MBTA Zero): 0

●

RTC may be accessed by the host (at default)

— Bit 5 (RTC Lock Default): 0

●

Flash is not protected to allow debug

— Bits 9-7 (Flash Contents Protect): 111

●

Use RESET2 on pin IOPB7/RING/PFAIL/RESET2

— Bits 15-14 (RST2EN): 01

The value that should be written to the protection word is 7F9E16 (binary 0111 1111 1001 1110).

Example 2

Same as Example 1, but for production version, once all debugging is completed. Change bits 9-7 from 111 to 000. Thus

the value that should be written to the protection word is 7C1E16 (binary 0111 1100 0001 1110).

Example 3

●

Core boot block size is 8 Kbytes

— Bit 3-0 (Core Boot Block): 1101

●

Shared BIOS using an expansion memory

— Bit 4 (Host Boot Block): 1

— Bit 6 (Force MBTA Zero): 0

●

RTC may be accessed by the host (at default)

— Bit 5 (RTC Lock Default): 0

●

Flash is not protected to allow debug

— Bits 9-7 (Flash Contents Protect): 111

●

Use RESET2 on pin IOPD2/EXWINT24/RESET2

— Bits 15-14 (RST2EN): 10

The value that should be written to the protection word is BF9D16 (binary 1011 1111 1001 1101).

Example 4

●

Core boot block size is 4 Kbytes

— Bit 3-0 (Core Boot Block): 1110

●

Shared BIOS using an expansion memory

— Bit 4 (Host Boot Block): 1

— Bit 6 (Force MBTA Zero): 0

●

After reset, RTC may be accessed only by the core, and host access is blocked until host access is enabled by the

core.

— Bit 5 (RTC Lock Default): 1

●

Flash is not protected to allow debug

— Bits 9-7 (Flash Contents Protect): 111

●

Do not use RESET2 (only RESET1 is in use)

— Bits 15-14 (RST2EN): 11

The value that should be written to the protection word is FFBE16 (binary 1111 1111 1011 1110)..

PC87591L Datasheet(PDF) 435 Page - National Semiconductor (TI)

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