beautypg.com

Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual User Manual

Page 38

background image

Data Table

Chapter 3

3Ć11

Timer/Counter Preset Values, Bit/Word Storage

This area of memory is used to store preset values of timer/counter
instructions. The area may also be used as storage for words and/or bits.

Word addresses 130

8

to 177

8

bound this area when memory is configured

for 256 I/O (maximum) and 40 Timer/Counter Instructions (Figure 3.3).

NOTE: Each timer or counter used actually requires two words of data
table memory: one from the accumulated value area (030

8

to 077

8

) and the

other from the preset value area (130

8

to 177

8

).

Developing the Data Table

The data table configurations shown in Figure 3.2 should be used as a
guide when developing the data table. Determining the number of words
needed and assigning addresses is a procedure that requires care and
attention to detail. The data table should be roughed out in advance but
formally developed as you write your program. Data table documentation
forms, described in Section 3.4 and presented at the end of this section, or
their equivalent, should be used to keep track of each assigned data table
word and bit address.

Displaying the Data Table

To see the present configuration of the data table, press [SEARCH] [5] [4].
This action displays a diagram of the areas of memory including the data
table, user program, message area and the unused memory. The number of
words in each area is indicated in decimal.

To terminate this display, Press [CANCEL COMMAND] (Table 3.A).