AT89C5131A-RDTUM datasheet(48/188 Pages) ATMEL

48 / 188 page

4337K–USB–04/08

AT89C5130A/31A-M

11.5

Hardware Conditions

It is possible to force the controller to execute the bootloader after a Reset with hardware condi-

tions. Depending on the product type (low pin count or high pin count package), there are two

methods to apply the hardware conditions.

11.5.1

High Pin Count Hardware Conditions (PLCC52, QFP64)

For high pin count packages, the hardware conditons (EA = 1, PSEN = 0) are sampled during

the RESET rising edge to force the on-chip bootloader execution (See Figure 27-5 on page

172). In this way the bootloader can be carried out regardless of the user Flash memory content.

It is recommended to pull the PSEN pin down to ground though a 1K resistor to prevent the

PSEN pin from being damaged (see Figure 11-3 below).

Figure 11-3. ISP Hardware conditions

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

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

To ensure correct microcontroller startup, the PSEN pin should not be tied to ground during

power-on (see Figure 11-4 below).

Copy of the Device ID#3: Name and Revision

FFh

61h

Description

Default Value

Address

ALE

VCC

/PSEN

RST

GND

Unconnected

VCC

VSS

VCC

GND

Crystal

GND

XTAL2

XTAL1

Bootloader

GND

AT89C5131A-RDTUM Datasheet(PDF) 48 Page - ATMEL Corporation