PPC-2000 User’s Guide
Chapter 5: LogicPro and Modbus Reference
Doc.# 30002-00 Rev 2.3
Watlow Anafaze
215
Table 5.61
Program Version Information
Changed Data Queue
The
Changed Data Queue
is a tool for hosts which need to
maintain a mirror image database of the PPC-2000 database.
Typically, these are PC based hosts. Most simple operator
interfaces, such as operator interface terminals, constantly
query the PPC for only the information that needs to be
displayed on the current screen. These devices would not read
the queue.
The PPC-2000 can communicate with 1 or 2 host devices with
read/write capability. If 2 hosts are used, the changed data
queue alerts port 1 host that port 2 host has changed a
section(s) of the database and vice versa. Each port has a
dedicated queue which must be continuously monitored by the
respective host. The addresses are the same for both ports, but
the data in each queue may differ because port 1 queue
monitors port 2 activity while port 2 queue monitors port 1
activity.
The queue consists of a group of read-only registers. Register
33051 contains the quantity of parameters which have been
changed by the other host. Registers 33052-N form a first-in-
first-out stack of changed parameters consisting of the
parameter ID numbers. The queue does not report the changed
status of specific elements within a parameter but only the
parameter ID number that has been changed. Therefore, if the
changed data queue notifies host 1 that host 2 has changed a
parameter, it is necessary for host 1 to read all elements within
a parameter to update host 1's database.
Using a First In First Out (FIFO) stack, the queue logs all
changes to the database originating from another host.
Register 33052 contains the oldest change logged, 33053
contains the second oldest and so on. After the host reads the
register(s), the data is cleared and shifted in the FIFO stack.
Database Offset
Description
1
Major version, first digit
2
Major version, second digit
3
Minor version, first digit
4
Minor version, second digit
5
Release level alpha character
6
Reserved
7
Reserved
8
Reserved
Summary of Contents for Anafaze PPC-2000
Page 2: ......
Page 14: ...Table of Contents PPC 2000 User s Guide viii Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 24: ...List of Tables PPC User s Guide xviii Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 36: ...Chapter 1 Overview PPC 2000 User s Guide 12 Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 112: ...Chapter 2 Hardware Installation PPC 2000 User s Guide 88 Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 184: ...Chapter 4 Troubleshooting PPC 2000 User s Guide 158 Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 296: ...Chapter 7 Specifications PPC 2000 User s Guide 268 Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 310: ...Appendix A Modbus Protocol PPC 2000 User s Guide 282 Watlow Anafaze Doc 30002 00 Rev 2 3...
Page 311: ...Doc 30002 00 Rev 2 3 Watlow Anafaze 283 B Appendix B Declaration of Conformity...
Page 319: ...PPC 2000 User s Guide Glossary Doc 30002 00 Rev 2 3 Watlow Anafaze 291...
Page 320: ...Glossary PPC 2000 User s Guide 292 Watlow Anafaze Doc 30002 00 Rev 2 3...
