Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Bedienungsanleitung PDF herunterladen (Seite 121)

Full-Duplex Protocol

Chapter 10

1017

begin

GET-CHAR

if char is a DLE

begin

add char to BCC

return a DLE and a data flag

end

else if char is an ACK or NAK send it to the transmitter

else if char is an ETX

begin

GET-CHAR

add char to BCC

return ETX with a control flag

end

else return character with a control flag

end

GET-CHAR is defined as

an implementation dependent function that returns one byte of data from the link interface hardware.

Full-Duplex Protocol Diagrams

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

interfaces. Control characters are shown in bold type. Link–level data is

represented by xxxx. Line noise is represented by ???. BCC is shown at

the end of each message packet. Time is represented as increasing from

the top of the figure to the bottom. Figure 10.9 shows normal message

transfer.

Figure 10.9

Normal

Message T

ransfer

Not Full

DLE ACK

xxxx

DLE STX xxxx DLE ETX BCC

xxxx

SOURCE XMTR LINK RCVR SINK

110046–I

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Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Bedienungsanleitung Seite 121