
27
3-1
Introduction
There are several basic steps involved in writing a program. Sheets that can
be copied to aid in programming are provided in Appendix F I/O Assignment
Sheets and Appendix G Program Coding Sheet.
1, 2, 3.. 1.
Obtain a list of all I/O devices and the I/O points that have been as-
signed to them and prepare a table that shows the I/O bit allocated to
each I/O device.
2.
Determine what words are available for work bits and prepare a table in
which you can allocate these as you use them.
3.
Also prepare tables of TC numbers so that you can allocate these as
you use them. Remember, the function of a TC number can be defined
only once within the program. (TC numbers are described in 3-7-13 Tim-
ers and Counters.)
4.
Draw the ladder diagram.
5.
Input the program into the Programming Console.
6.
Check the program for syntax errors and correct these.
7.
Transfer the program from the Programming Console to the CPU and
execute the program to check for execution errors and correct these.
8.
After the entire Control System has been installed and is ready for use,
execute the program and fine tune it if required.
3-2
Memory Areas
Details, including the name, acronym, range, and function of each area are
summarized in the following table. All but the last area are data areas. Data
and memory areas are normally referred to by their acronyms. Bits not listed
in the following table cannot be used.
Area
PC
No. of
bits
Word
addresses
Bit
addresses
Function
Input bits
SP10
6
00
0000 to 0005
Input external signals to the PC. These bits can be
used as many times as required in the program.
SP16
10
00
0000 to 0009
SP20
12
00
0000 to 0011
Output bits
SP10
4
01
0100 to 0103
Each of these bits can be used in only one instruction
controlling its status, but can be used as many times as
required in other instructions. If the status of the same
output bit is controlled by more than one instruction,
only the status determined by the last instruction will be
output.
SP16
6
01
0100 to 0105
SP20
8
01
0100 to 0107
Memory Areas
Section 3-2