Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Uživatelský manuál stáhnout pdf (Strana 142)

Half-Duplex Protocol

Chapter 11

1115

Figure 11.6 shows a message transfer in which the acknowledgment was

destroyed by noise. After a timeout, the message is retransmitted and the

DLE ACK response is detected.

Figure 11.6

Message

Transfer with ACK Destroyed

Not Full

xxxx

SINK MASTER LINK SLAVE SINK

10056–I

DLE ACK

SOURCE/ SOURCE/

DLE STX xxxx DLE ETX BCCDLE SOH STN

(Timeout)

DL ??? CK

DLE STX xxxx DLE ETX BCCDLE SOH STN

Figure 11.7 shows a slave being polled, and responding with DLE EOT

because it has no messages to transfer.

Figure 11.7

Poll

with No Message A

vailable

No Message

Not Full

SINK MASTER LINK SLAVE SINK

10057–I

DLE EOT

SOURCE/ SOURCE/

BCCDLE ENQSTN

1 2 ... 137 138 139 140 141 142 143 144 145 146 147 ... 238 239

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Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Uživatelský manuál Strana 142