AT89C5132-ROTIL datasheet(6/33 Pages) ATMEL

6 / 33 page

4256B–USB–03/06

AT89C5132

In-System

Programming

The ISP allows the user to program or reprogram the microcontroller’s on-chip Flash memory

through the serial line without removing it from the system and without the need of a pre-pro-

grammed application.

This section describes how to start the USB bootloader and the higher level protocol.

Bootloader

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 F000h to FFFFh. The

boot memory is enabled by setting the ENBOOT bit in AUXR1 (see Table 4). The three ways to

set this bit are detailed below.

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.

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 2, the hardware condition always allows In-System recovery when user’s

memory has been corrupted.

Programmed

Condition Boot

Mapping

The programmed condition is based on the Bootloader Jump Bit (BLJB) in HSB (see Table 5).

As shown in Figure 2, 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 exe-

cute the bootloader software.

AT89C5132-ROTIL Datasheet(PDF) 6 Page - ATMEL Corporation