Table of Contents
iii
Ethernet Communications Modules, 3rd Edition, Rev. D
Chapter 4 - RLL Programming for Communications
PLC-to-PLC Communications .....................................................................................4–2
How RLL is Used for Communications ...................................................................... 4–2
Network Instructions ................................................................................................. 4–3
Read (RX) and Write (WX) Instructions .....................................................................4–3
Building the Read (RX) and Write (WX) Routine ....................................................... 4–3
The First LD Instruction ............................................................................................4–3
The Second LD Instruction .......................................................................................4–4
The LDA Instruction .................................................................................................4–4
Read (WX) Instruction ..............................................................................................4–5
Write (WX) Instruction .............................................................................................4–5
Addressing the Different Memory ........................................................................... 4–6
Bit Memory ............................................................................................................. 4–6
Word Memory and Aliases ........................................................................................4–6
DirectSOFT is Flexible ..............................................................................................4–7
DL05 CPU ................................................................................................................4–7
DL06 CPU ................................................................................................................4–7
D2-240 CPU .............................................................................................................4–8
D2-250-1 CPU ..........................................................................................................4–8
D2-260/D2-262 CPU ................................................................................................4–9
D4-430 CPU .............................................................................................................4–9
D4-440 CPU ...........................................................................................................4–10
D4-450/D4-454 CPU ..............................................................................................4–10
Special Relays for Communications ........................................................................4–11
Program with One Read Instruction ....................................................................... 4–13
Program for the Initiating PLC ................................................................................4–13
Program for the Responding PLC ...........................................................................4–13
Example Program with One Write Instruction ....................................................... 4–15
Program for the Initiating PLC ................................................................................4–15
Program for the Responding PLC ...........................................................................4–15
Integrating Multiple Read and Write Instructions .................................................4–17
Interlocking Relays ..................................................................................................4–17
First RX/WX Instruction ..........................................................................................4–18
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