Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Instrukcja Użytkownika Pobierz pdf (Strona 47)

Asynchronous Link Protocols

Chapter 4

4-4

Figure 4.1

Packet

Format for Full-Duplex Protocol

CMD STS Command/Response Block

DST SRC CMD STS TNS

Data

(From Application Layer)

DLE STX

Data

(From Network Layer)

DLE ETX

From

Application

Layer

From

Network

Layer

11321A

BCC Data Link

Layer Packet

Block Check

The block check character (BCC) is a means of checking the accuracy of

each message packet transmission. It is the 2’s complement of the 8-bit

sum (modulo-256 arithmetic sum) of all data bytes between the DLE STX

and the DLE ETX BCC. It does not include any other message packet

codes or response codes.

Example 1: If a message packet contained the data codes 08, 09, 06, 00,

02, 04 and 03, the message packet codes would be (in hex):

DLE STX

02 08 09 06 00 02 04 03 10 03 E0

DLE ETX BCCData

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 234 235

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Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Instrukcja Użytkownika Strona 47