Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Instrukcja Użytkownika Pobierz pdf (Strona 126)

Full-Duplex Protocol

Chapter 10

1022

If you were to connect a line monitor to the wires between station A and

B, and only the A to B subsystem were active, you could observe the

following:

Examples

Normal Message

Path 1: DLE STX xxxDLE ETX BCC DLE STXxxxxDLE ETX BCC

Path 2: DLE ACK DLE ACK

Message with parity or BCC error and recovery

Path 1: DLE STXxx???xxDLE ETX BCC DLE STXxxxxDLE ETX BCC

Path 2: DLE NAK DLE ACK

Message with ETX destroyed

Path 1: DLE STXxxxxx????[timeout] DLE ENQ DLE STXxxxxDLE ETX BCC

Path 2: DLE NAK DLE ACK

Good message but ACK destroyed

Path 1: DLE STXxxxDLE ETX BCC [timeout] DLE ENQ DLE STXxxx etc.

Path 2: DL???CK DLE ACK

Messages being sent in both directions

Path 1: DLE STXxxxDLE ETX BCC DLE STXxxxxDLE ETX BCC DLE STX

Path 2: DLE ACK DLE ACK

Path 3: DLE STXxxx xxxxDLE ETX BCC DLE STX

Path 4: DLE ACK

Combined –

Circuit AB:DLE STXxxxDLE ETX BCC DLE STXxxxxDLE ETX BCC DLE ACK DLE STX

Circuit BA: DLE STXxxxDLE ACKxxxxDLE ETX BCC DLE ACK DLE STX

embedded response

ACK on AB delayed slightly because ETX BCC are indivisible

1 2 ... 121 122 123 124 125 126 127 128 129 130 131 ... 238 239

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Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Instrukcja Użytkownika Strona 126