Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 78)

Advanced Instruction Set
Chapter 6
6Ć21
Figure 6.10
Types of file Instructions
DN
WordĆToĆFile Move
Counter Addr:
Position:
File Length:
Word Addr:
File R: 007
012
113
420- 433
DN
212
212
15
EN
FileĆToĆFile Move
Counter Adddr:
Position:
File Length:
File A:
File R: 001
014
512- 527
562- 577
214
214
17
Rate Per Scan: 014
214
15
Externally Indexed FIle Instruction
Internally Indexed File Instruction
Externally Indexed
Externally indexed means that you assign an accumulated value to the counter.
The counter address is the same address as the file instruction in the
accumulated value area of the data table. The counter address hold the
accumulated value. The accumulated value points to the file’s position value.
The position value is the accumulated value and it represents the specific word
location within the file.
Another characteristic of the externally indexed file instruction is that it only
has a done bit. This is bit 15. the done bit is automatically entered from the
counter address. It is set when the operation is complete and remains set as long
as the rung condition is true.
Internally Indexed
Internally indexed means that the accumulated value of the counter is internally
incremented. You again assign an accumulated value to the counter.
When you look at Figure 6.10 notice that a value for rate per scan is needed.
The rate per scan defines the number of words which will be operated upon
during one scan. For example, suppose you have a file that contains twelve
words. If you assign the value of 004 for the rate per scan that means that the
instruction will execute four words per scan at a time. Therefore, the entire
operation will be completed in three scans.