Omron CVM1D, Operation Manual

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90
When drawing ladder diagrams, it is important to keep in mind the number of
instructions that will be required to input it. In diagram A, below, an OR LOAD
instruction will be required to combine the top and bottom instruction lines. This
can be avoided by redrawing as shown in diagram B so that no AND LOAD or OR
LOAD instructions are required. Refer to 5-6-5 AND LOAD and OR LOAD for
more details and 4-4-1 Logic Block Instructions for further examples of diagrams
requiring AND LOAD and OR LOAD.
Diagram A
Diagram B
Address Instruction
00000 LD 000000
00001 LD 000001
00002 AND 000207
00003 OR LD ---
00004 OUT 000207
Address Instruction
00000 LD 000001
00001 AND 000207
00002 OR 000000
00003 OUT 000207
Operands
Operands
0000
01
0002
07
0000
00
0000
01
0002
07
0000
00
0002
07
0002
07
4-11 Program Execution
When execution or a ladder diagram is started, the CPU scans the program from
top to bottom, checking all conditions and executing all instructions accordingly
as it moves down the bus bar. It is important that instructions be placed in the
proper order so that, for example, the desired data is moved to a word before that
word is used as the operand for an instruction. Remember that an instruction line
is completed to the terminal instruction at the right before executing instruction
lines branching from the first instruction line to other terminal instructions at the
right.
Program execution is only one of the tasks carried out by the CPU as part of the
cycle time. Refer to Section 6 Program Execution Timing for details.
4-12 Data Formats
The following data formats can be handled by the various calculation and con-
version instructions.
•
Unsigned binary
•
Signed binary
•
Unsigned BCD
•
Signed BCD
•
Floating-point
4-12-1 Unsigned Binary Data
Data is configured in words, with 16 bits per word. This data is regarded as 16-bit
binary data. Unsigned binary data is often written as four-digit hexadecimal
(0000 to FFFF).
Bit 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
2
15
2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
2
3
2
2
2
1
2
0
2
3
2
2
2
1
2
0
2
3
2
2
2
1
2
0
2
3
2
2
2
1
2
0
Digit 16
3
16
2
16
1
16
0
Data Formats
Section 4-12