UPD77533 datasheet(51/104 Pages) RENESAS

51 / 104 page

Data Sheet S15671EJ4V0DS

µµµµPD77533

15.1.1 Server command analysis

The host CPU analyzes server commands sent by the LS as follows.

(1) Checks whether the command header is the “$” character.

(2) Checks whether the command ID is valid. Starts the checksum calculation.

(3) Calculates the number of bytes in the data field according to “Determination of Number of Bytes in Data Field”

in Table 15-2.

(4) Reads data of the number of bytes calculated in (3) and calculates the checksum.

(5) Checks whether the checksum matches the calculated value.

(6) Checks whether the end-of-packet is <CR><LF>.

If all of (1) to (6) are OK, the command is recognized as one command.

If the command is other than the baud rate change command, the command is packeted and transferred to the

µPD77533. If an error occurs at any stage, 1 byte is discarded and the operation starts again from (1).

Table 15-2. Determination of Number of Bytes in Data Field

Command ID

Determination of Number of Bytes in Data Field

Fixed to 0 bytes

Fixed to 1 byte

Value stored in first 2 bytes of data field minus 7 bytes

Fixed to 1 byte

Value stored in first 2 bytes of data field minus 7 bytes

Fixed to 5 bytes

Fixed to 0 bytes

Fixed to 4 bytes

Fixed to 0 bytes

Fixed to 1 byte

Fixed to 9 bytes

Fixed to 1 byte

Value stored in first 2 bytes of data field minus 7 bytes

Fixed to 1 byte

Fixed to 4 bytes

Value stored in first 2 bytes of data field minus 7 bytes

Fixed to 1 byte

Fixed to 3 bytes

If previous !fa result code is 0: Fixed to 2050 bytes

If previous !fa result code is 1: Fixed to 1026 bytes

Fixed to 1 byte

Fixed to 2 bytes

Fixed to 10 bytes

UPD77533 датащи(PDF) 51 Page - Renesas Technology Corp