Datasheet

126
AT89C51ID2
4289C–8051–11/05
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
choosen 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 50. 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
Record
Load
Data
Mark
’:’
Reclen
Offset
Type
or
Info
Checksum
1-byte
1-byte
2-bytes
1-byte
n-bytes 1-byte