AT89C5131A-RDTIL datasheet(44/186 Pages) ATMEL

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AT89C5131A-L

4338F–USB–08/07

Boot Process

Software Boot Process

Example

Many algorithms can be used for the software boot process. Below are descriptions of

the different flags and Bytes.

Boot Loader Jump bit (BLJB):

- This bit indicates if on RESET the user wants to jump to this application at address

@0000h on FM0 or execute the boot loader at address @F400h on FM1.

- BLJB = 0 (i.e. bootloader FM1 executed after a reset) is the default Atmel factory pro-

gramming.

-To read or modify this bit, the APIs are used.

Boot Vector Address (SBV):

- This byte contains the MSB of the user boot loader address in FM0.

- The default value of SBV is FFh (no user boot loader in FM0).

- To read or modify this byte, the APIs are used.

Extra Byte (EB) & Boot Status Byte (BSB):

- These Bytes are reserved for customer use.

- To read or modify these Bytes, the APIs are used.

Figure 23. Hardware Boot Process Algorithm

RESET

BLJB == 0

Bootloader

in FM1

Application

in FM0

bit ENBOOT in AUXR1 Register

Is Initialized with BLJB Inverted.

ENBOOT = 0

PC = 0000h

ENBOOT = 1

PC = F400h

Example, if BLJB=0, ENBOOT

is set (=1) during reset, thus the

bootloader is executed after the

reset.

AT89C5131A-RDTIL 数据表(PDF) 44 Page - ATMEL Corporation

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