AT89C5131A-RDTUL datasheet(46/186 Pages) ATMEL

46 / 186 page

AT89C5131A-L

4338F–USB–08/07

As PSEN is an output port in normal operating mode (running user application or boot-

loader code) after reset, it is recommended to release PSEN after rising edge of reset

signal.

Low Pin Count Hardware

Conditions (SOIC28)

Low pin count products do not have PSEN signal, thus for these products, the boot-

loader is always executed after reset thanks to the BLJB bit. The Hardware Conditions

are detected at the begining of the bootloader execution from reset.

The default factory Hardware Condition is assigned to port P1.

•

P1 must be equal to FEh

In order to offer the best flexibility, the user can define its own Hardware Condition on

one of the following Ports:

•

Port1

•

Port3

•

Port4 (only bit0 and bit1)

The Hardware Conditions configuration is stored in three bytes called P1_CF, P3_CF,

P4_CF.

These bytes can be modified by the user through a set of API or through an ISP

command.

Note:

1. The BLJB must be at 0 (programmed) to be able to restart the bootloader.

2. BLJB can always be changed by the means of API, whether it's a low or high pin

count package.But for a low pin count version, if BLJB=1, no ISP via the Bootloader

is further possible (because the HW conditions are never evaluated, as described in

the USB Bootloader Datasheet). To go back to ISP, BLJB needs to be changed by a

parallel programmer(or by the APIs).

See a detailed description in the applicable Document.

–

Datasheet Bootloader USB AT89C5131.

AT89C5131A-RDTUL датащи(PDF) 46 Page - ATMEL Corporation