Rockwell Automation 1785-L20C_L40C, D17856.5.14 ControlNet PLC-5 Programmable Controllers User Manual User Manual

Page 34

Chapter 2

Planning to Use Your ControlNet

PLCĆ5 Processor

2-6

ControlNet Data Transfer

Private

Memory

Buffers

Housekeeping

Logic Scan

Program Scan

DataĆ

Table

Files

Immediate Data Transfer

ЙЙ

= Unscheduled Data Transfer

= Scheduled Data Transfer

ЗЗ

ЙЙ

= NUI

Data Update

Table 2.C

ControlNet Immediate DataĆTransfer Operations

Instructions

Description

Immediate I/OĊControlNet and Remote I/O

001

(

)

IIN

001

(

)

IOT

In the case of an IIN, the most recent copy of the specified input word secured in the last discrete I/O

data transfer from the corresponding I/O chassis is used. This value is moved from the private memory

buffer to the working data table and is used in all subsequent ladder instructions. This data could be as

old as the time taken since the last asynchronous I/O update, and it may not actually reflect the latest

state of the input word.
In the case of an IOT, the current state of the specified output word is copied to the private memory

buffer and is used on the next output update to the I/O chassis. The actual change is not

communicated until the next asynchronous I/O transfer.
Only 1 word of I/O data can be updated per instruction.

ControlNet Immediate Data I/O

IDI

IMMEDIATE DATA INPUT

Data file offset

Length

232

Destination

N11:232

IDO

IMMEDIATE DATA OUTPUT

Data file offset

Length

175

Source

N12:175

The ControlNet Immediate Data I/O instructions work in much the same way as the immediate I/O

instructions. During an input instruction, the most recent data is copied from the private memory buffer

to a dataĆtable address that you specify. In the case of an output instruction, the data is copied from an

area that you specified to the private memory buffer and sent on the next I/O update.
As many as 64 words can be transferred per instruction.

Important: In most cases, you should set the Data file offset and the SourceĊof an IDOĊor the Data

file offset and the DestinationĊof an IDIĊto the same address. See page

4Ć6

for more information on

this and other aspects of using ControlNet IDI and IDO instructions.