Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Instrukcja Użytkownika Pobierz pdf (Strona 54)

Data Highway Communication

Chapter 3

39

A PLC–3 station can read from any part of a PLC/PLC–2 data table.

However, A PLC– 3 station cannot write to a PLC/PLC–2 if the switch

settings at the PLC/PLC–2 station forbid access. If the switches at the

PLC/PLC–2 station are set to accept only protected write commands, then

the ladder diagram program at the PLC/PLC–2 station must contain

memory access rungs to define which areas of the PLC/PLC–2 station’s

data table are accessible. In such a case, a transmitting PLC–3 station can

write to only those data table areas defined by the memory access rungs,

and only by means of protected write commands. If the switches at the

PLC/PLC–2 station are set to accept unprotected write commands, a

PLC–3 station can then write to any area of the PLC/PLC–2’s data table

by transmitting an unprotected write command (section titled Command

Message Type chapter 6).

Accessing a PLC–3 from a PLC/PLC–2 Processor

While a PLC–3 processor can address any area of a PLC/PLC–2 data

table, a PLC/PLC–2 reads an input file that is a part of the PLC–3 data

table. That file is the PLC–3 input file with a number that corresponds to

the station number of the PLC/PLC–2 station. For example, the

read/write files assigned to PLC/PLC–2 stations 1 to 100 (octal) would be

as follows:

PLC/PLC-2

Station

Number (octal)

Assigned PLC-3 Input File

for Read/W

rite Access

000 I008

[1]

001 I001

002 I002

003 I003

004 I004

005 I005

006 I006

007 I007

010 I010

011 I011

012 I012

. .

077 I077

100 I100

[1]

Station address 000 is assigned to input file I008. Otherwise PLC-3 input

files with an 8 or 9 in their address are not used for read/write access by a

PLC-PLC-2 station (except I008 for station 0).

1 2 ... 49 50 51 52 53 54 55 56 57 58 59 ... 238 239

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