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MELSEC-Q/QnA
3 CONFIGURATION OF INSTRUCTIONS
3.8 Counting Step Number
The number of steps in CPU module sequence instructions, basic instructions, and application
instructions differs depending on whether indirect setting of the device used is possible or not.
The basic number of steps for basic instructions and application instructions is calculated by
adding the device number and 1.
For example, the "+ instruction" would be calculated as follows:
D0 R0 D10
4 steps
+D0 R0
3 steps
+
Indicates the number of devices
1
2 3
2
1
(1) Conditions for increasing the number of steps
The number of steps is increased over the number of basic steps in cases where a device is
used that is designated indirectly or for which the number of steps is increased.
(a) When device is designated indirectly
In cases where indirect designation is done by @
, the number of steps is increased
1 step over the number of basic steps.
For example, when a 3-step MOV instruction is designated indirectly (example: MOV K4X0
@D0), one step is added and the instruction becomes 4 steps.
(b) Devices where number of steps increases
Devices Where Number of Steps
Increases
Added Steps Example
Intelligent function module
device/special function module
device
MOV U4\G10 D0
Link direct devices MOV J3\B20 D0
Serial number access file registers MOV ZR123 D0
32-bit constants DMOV K123 D0
Real number constant
1
EMOV E0.1 D0
Character string constant
For even numbers:
(number of characters)/2
For odd numbers:
(number of characters + 1)/2
$MOV "123" D0
(c) In cases where the conditions described in (a) and (b) above overlap, the number of steps
becomes a culmination of the two.
For example, if MOV U1\G10 ZR123
has been designated, 1 step is added for buffer
register designation and 1 step is added for serial number access file register designation,
making a total of 2 steps added.
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