AT89C51ED2-RDTUM datasheet(102/137 Pages) ATMEL

102 / 137 page

102

4235K–8051–05/08

AT89C51RD2/ED2

24.7

ISP Protocol Description

24.7.1

Physical Layer

The UART used to transmit information has the following configuration:

• Character: 8-bit data

• Parity: none

• Stop: 2 bits

• Flow control: none

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

host.

24.7.2

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.

Figure 24-6. Intel Hex Type Frame

• Record Mark:

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

• Reclen:

Reclen specifies the number of bytes of information or data which follows 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 Data Program Record (see Section “ISP Commands Summary”).

• Record Type:

Record Type specifies the command type. This field is used to interpret the remaining informa-

tion within the frame. The encoding for all the current record types is described in Section “ISP

Commands Summary”.

• Data/Info:

Data/Info is a variable length field. It consists of zero or more bytes encoded as pairs of hexa-

decimal digits. The meaning of data depends on the Record Type.

• Checksum:

The two’s complement of the 8-bit bytes that result from converting each pair of ASCII hexadec-

imal digits to one byte of binary, and including the Reclen field to and including the last byte of

the Data/Info field. Therefore, the sum of all the ASCII pairs in a record after converting to

binary, from the Reclen field to and including the Checksum field, is zero.

Record

Load

Data

Mark

’:’

Reclen

Offset

Type

Info

Checksum

1-byte

2-bytes

1-byte

n-bytes

1-byte

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