AT89C51ED2-RDTUM datasheet(104/137 Pages) ATMEL

104 / 137 page

104

4235K–8051–05/08

AT89C51RD2/ED2

• SBV = FCh

• SSB = FFh

The Full Chip Erase does not affect the bootloader.

24.8.3

Checksum Error

When a checksum error is detected, send ‘X’ followed with CR&LF.

24.9

Flow Description

24.9.1

Overview

An initialization step must be performed after each Reset. After microcontroller reset, the boot-

loader waits for an autobaud sequence (see section ‘Autobaud Performances’).

When the communication is initialized, the protocol depends on the record type requested by the

host.

FLIP, a software utility to implement ISP programming with a PC, is available from the Atmel

web site.

24.9.2

Communication Initialization

The host initializes the communication by sending a ’U’ character to help the bootloader to com-

pute the baudrate (autobaud).

Figure 24-7. Initialization

24.9.3

Autobaud Performances

The ISP feature allows a wide range of baud rates in the user application. It is also adaptable to

a wide range of oscillator frequencies. This is accomplished by measuring the bit-time of a single

bit in a received character. This information is then used to program the baud rate in terms of

timer counts based on the oscillator frequency. The ISP feature requires that an initial character

(an uppercase U) be sent to the AT89C51RD2/ED2 to establish the baud rate. Table show the

autobaud capability.

Host

Bootloader

"U"

Performs Autobaud

Init Communication

If (Not Received "U")

"U"

Communication Opened

Else

Sends Back “U” Character

Table 24-8.

Autobaud Performances

Frequency

(MHz)

Baudrate (kHz)

1.8432

2.4576

3.6864

7.3728

2400

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