AT89C51ED2-RDTIM datasheet(104/137 Pages) ATMEL

104 / 137 page

104

AT89C51RD2/ED2

4235E–8051–04/04

ISP Protocol Description

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.

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 45. 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

information 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

hexadecimal 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

hexadecimal 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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