T83C5121 datasheet(67/110 Pages) ATMEL

67 / 110 page

T8xC5121

4164E–SCR–02/04

Table 49. Valid Software Security Byte Values

UART Protocol

Overview

The serial protocol used is described below.

Physical Layer

The UART is used to transmit information with the following configuration:

•

Character: 8-bit data

•

Parity: none

•

Stop: 1 bit

•

Flow control: none

•

Baudrate: autobaud is performed by the bootloader to compute the baudrate

chosen by the host.

Datas and Limits

As described in Section “Transfer Checks”, the downloaded program include the CRC

values in the last two upper bytes of the 16K bytes space.

An update of a part of the 16K program cannot be done because the CRC value would

have to be updated with a value which depends of the actual value of the rest of the

program.

So the Program function of the PC Software Tool include the individual program com-

mands (with 64 data bytes) from address 0000h to address 3FFFh.

Frame Description

The Serial Protocol is based on the Intel Hex-type records.

Intel Hex records consist of ASCII characters used to represent hexadecimal values and

are summarized below:

Table 50. Intel Hex Type Frame

•

Record Mark:

–

Record Mark is the start of frame. This field must contain’:’.

•

Reclen:

–

Reclen specifies that the number of bytes of information or data that follow

the Record Type field of the record.

•

Load Offset:

–

Load Offset specifies the 16-bit starting load offset of the data bytes,

therefore this field is used only for Program Data Record (see Table 51).

SSB Values

Functions

No bypass and level1 security

No bypass and level2 security

BF,BE,BC

UART bypass and security levels

7F,7E,7C

External TWI bypass and security levels

3F,3E,3C

UART and Ext. TWI bypass

Record Mark ‘:’

Reclen

Load Offset

Record Type

Data or Info

Checksum

1-byte

1-byte = 40h

2-byte

1-byte

64-byte

1-byte

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