Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Uživatelský manuál stáhnout pdf (Strana 75)

Asynchronous Link Protocols

Chapter 4

4-32

When a DLE NAK is received, the transceiver takes messages from the

source until it is empty. Each message will be discarded with an error

code sent back to the message source. This can be used by the master to

clear up the message source buffers of all slaves after the master has been

down.

Half-Duplex Protocol Diagrams

The following figures show some of the events that occur on various

interfaces. Time is represented as increasing from the top of the figure to

the bottom.

Figure 4.17

Normal

Message T

ransfer

Not Full

xxxx

SINK MASTER LINK SLAVE SINK

11567

DLE ACK

DLE STX xxxx DLE ETX BCC

SOURCE/ SOURCE/

DLE SOH STN

Figure 4.18

Message T

ransfer with Invalid BCC

Not Full

xxxx

SINK MASTER LINK SLAVE SINK

11568

DLE ACK

DLE STX ??? DLE ETX BCC

SOURCE/ SOURCE/

DLE SOH STN

DLE STX xxxx DLE ETX BCCDLE SOH STN

(Timeout)

1 2 ... 70 71 72 73 74 75 76 77 78 79 80 ... 234 235

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Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Uživatelský manuál Strana 75