T89C5115-RATIM datasheet(46/113 Pages) ATMEL

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AT89C5115

4128F–8051–05/06

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 @F800h 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 FCh (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 19. Hardware Boot Process Algorithm

Application-

Programming-Interface

Several Application Program Interface (API) calls are available for use by an application

program to permit selective erasing and programming of Flash pages. All calls are made

by functions.

All these APIs are described in detail in the following documents on the Atmel web site.

–

Datasheet Bootloader UART T89C5115.

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 = F800h

Example, if BLJB=0, ENBOOT

is set (=1) during reset, thus the

bootloader is executed after the

reset.

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