Allen-Bradley PLC-5 - Page 6

Publication 1785-UM012D-EN-P - July 2005
Table of Contents 2
Chapter 4
Addressing I/O and Controller
Memory
Using This Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
I/O Addressing Concept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Choosing an Addressing Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Addressing Block-Transfer Modules. . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Addressing Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Assigning Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Understanding PLC-5 Controller Memory. . . . . . . . . . . . . . . . . . . . 4-10
Understanding Data Storage (Data-Table Files) . . . . . . . . . . . . 4-11
Addressing File Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Understanding Program-File Storage . . . . . . . . . . . . . . . . . . . . . 4-15
Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Specifying I/O Image Addresses . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Specifying Logical Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
Specifying Indirect Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
Specifying Indexed Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
Specifying Symbolic Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
Optimizing Instruction Execution Time
and Controller Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
Effectively Using I/O Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Chapter 5
Communicating with
Controller-Resident I/O
Using This Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Introduction to PLC-5 Controller Scanning. . . . . . . . . . . . . . . . . . . . 5-1
Program Scanning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Transferring Data to Controller-Resident I/O. . . . . . . . . . . . . . . . . . 5-3
Transferring Discrete Data to Controller-Resident I/O . . . . . . . 5-3
Transferring Immediate I/O Requests. . . . . . . . . . . . . . . . . . . . . 5-3
Transferring Block-Transfer Data to Controller-Resident I/O . 5-4
Configuring the System for Controller-Resident I/O . . . . . . . . . . . . 5-4
Chapter 6
Communicating with Remote I/O Using This Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Selecting Devices That You Can Connect . . . . . . . . . . . . . . . . . . . . . 6-2
Introduction to Remote I/O. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Designing a Remote I/O Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
Configuring a Controller Channel as a Scanner . . . . . . . . . . . . . . . . . 6-6
Define an I/O Status File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Specify Channel Configuration Information . . . . . . . . . . . . . . . . 6-7
Specify the Scan List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9
Communicating to a Remote I/O Node Adapter . . . . . . . . . . . . . . 6-11
Troubleshooting Remote I/O Communication Difficulties. . . 6-12
Transferring Block Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13
Block-Transfers of Remote I/O Data . . . . . . . . . . . . . . . . . . . . . . . 6-15
Block-Transfer Sequence with Status Bits . . . . . . . . . . . . . . . . . . . . 6-17