Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Manual de usuario descargar pdf (Pagina 49)

Asynchronous Link Protocols

Chapter 4

4-6

1010 0000 0000 0001

As each additional byte is transmitted, it is included in the value in the

first) as the CRC field.

The receiver also calculates the CRC value and compares it to the

received CRC value to verify the accuracy of the data received.

Two-Way Simultaneous Operation

On a two-way simultaneous link there are only two physical circuits

connecting 4 distinct and independent programs. Referring to the diagram

below, Transmitter A and Receiver B manage the transfer of messages

from Station A to Station B by sending message packets from A to B and

returning responses from B to A. At the same time, Transmitter B and

Receiver A carry out the transfer of messages from Station B to Station A

by sending message packets from B to A and returning responses from A

to B.

Figure 4.2 shows the four independent data paths involved.

Figure 4.2

Data

Paths for T

wo-W

ay Simultaneous Operation

Transmitter

Receiver

Path 1

11556

Receiver

Transmitter

Path 3

Path 2

Path 4

Path 1 carries message codes from A to B; Path 2 carries response codes

from B to A; Path 3 carries message codes from B to A; and Path 4 carries

response codes from A to B.

1 2 ... 44 45 46 47 48 49 50 51 52 53 54 ... 234 235

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Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Manual de usuario Pagina 49