AT89C5132-ROTUL datasheet(19/181 Pages) ATMEL

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4173D–USB–02/06

AT89C5132

7.3

Boot Memory Execution

As internal C51 code space is limited to 64K Bytes, some mechanisms are implemented to allow

boot memory to be mapped in the code space for execution at addresses from F000h to FFFFh.

The boot memory is enabled by setting the ENBOOT bit in AUXR1 (see Table 6). The three

ways to set this bit are detailed in the following sections.

7.3.1

Software Boot Mapping

The software way to set ENBOOT consists in writing to AUXR1 from the user’s software. This

enables bootloader or API routines execution.

7.3.2

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

bootloader software.

As shown in Figure 7-3, the hardware condition always allows in-system recovery when user’s

memory has been corrupted.

7.3.3

Programmed Condition Boot Mapping

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

Figure 7-3, when this bit is programmed (by hardware or software programming mode), the chip

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

bootloader software.

Figure 7-3.

Hardware Boot Process Algorithm

The software process (bootloader) is detailed in the AT89C5132 Bootloader datasheet.

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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