AT89C5131A-RDTUM datasheet(49/188 Pages) ATMEL

49 / 188 page

4337K–USB–04/08

AT89C5130A/31A-M

Figure 11-4. Hardware conditions typical sequence during power-on.

11.5.2

Low Pin Count Hardware Conditions (QFN32)

Low pin count products do not have PSEN signal, thus for these products, the bootloader is

always executed after reset thanks to the BLJB bit. The Hardware Condition 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 Condition configuration are 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 pack-

age.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.

VCC

PSEN

RST

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