FANUC Robotics America GFK-1541B User Manual

The figure and text below explains how a Communications Request is executed.  The figure
specifically illustrates the successful operation of an Establish Read Channel command.

  

Client

Series 90-70

PLC CPU

Backplane

Ethernet
Interface

Server

Ethernet Interface

LAN

Power flows to COMMREQ
in ladder program

Command Block sent to
Interface

Verify
Command Block
and set up channel
to server PLC

Read Request

Data

Data

Read Request

Data

Data

Client

Data

Data

COMMREQ
Status Word

Return COMMREQ
Status (CRS) Word
to CPU

.
.
.

.
.
.

Read Request

Data

Data

Data

Pulse Data Transfer bit

Data Transfer

Pulse Data Transfer bit

Pulse Data Transfer bit

Data

Domain of a channel

Domain of a TCP connection

pulse received

Data Transfer

pulse received

Data Transfer

pulse received

Domain of a remote server

Server

CPU

Backplane

Read Request

Data

Read Request

Data

Read Request

Data

PLC

PLC

1.

A Communications Request begins when there is power flow to a COMMREQ function in
the client PLC.  At this time, the Command Block data is sent from the PLC CPU to the
Ethernet Interface.

2.

For the Establish Read Channel command, the COMMREQ Status word (CRS word) is
returned immediately if the Command Block is invalid.  If the syntax is correct, then the CRS
word is returned after the first significant event:  upon failure to establish a channel correctly
and in a timely manner or upon the first successful transfer of data.

Once the channel is successfully set up to the server PLC, the Ethernet Interface performs the
periodic reads as specified in the Command Block.

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