AT83SND2CMP3B datasheet(21/241 Pages) ATMEL

21 / 241 page

4341F–MP3–03/06

AT8xC51SND2C/MP3B

6.4.2

Hardware Condition Boot Mapping

The hardware condition is based on the ISP pin. When driving this pin to low level, the chip reset

sets ENBOOT and forces the reset vector to F000h instead of 0000h in order to execute the

boot loader software.

As shown in Figure 6-4 the hardware condition always allows in-system recovery when user’s

memory has been corrupted.

6.4.3

Programmed Condition Boot Mapping

The programmed condition is based on the Boot Loader Jump Bit (BLJB) in HSB. As shown in

Figure 6-4 when this bit is programmed (by hardware or software programming mode), the chip

reset set ENBOOT and forces the reset vector to F000h instead of 0000h, in order to execute

the boot loader software.

Figure 6-4.

Hardware Boot Process Algorithm

The software process (boot loader) is detailed in the “Boot Loader Datasheet” Document.

6.5

Preventing Flash Corruption

See Section “Reset Recommendation to Prevent Flash Corruption”, page 48.

Atmel’s

Boot Loader

Hard Cond?

ISP = L?

RESET

Hard Cond Init

ENBOOT = 1

PC = F000h

FCON = 00h

Prog Cond?

BLJB = P?

Standard Init

ENBOOT = 0

PC = 0000h

FCON = F0h

Prog Cond Init

ENBOOT = 1

PC = F000h

FCON = F0h

User’s

Application

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