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
bit ENBOOT in AUXR1 Register
Is Initialized with BLJB Inverted.
RESET
Example, if BLJB=0, ENBOOT
is set (=1) during reset, thus the
bootloader is executed after the
reset.
ENBOOT = 0
PC = 0000h
BLJB == 0
?
ENBOOT = 1
PC = F800h
Application
in FM0
Bootloader
in FM1
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.
46
AT89C5115
4128F–8051–05/06
ATMEL [ ATMEL ]
