Mitsubishi Electric MELSEC-Q Series User Manual page 164

10 DEVICES
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(2) Reading the inputs
(a) There are 2 types of input: "refresh inputs" and "direct access inputs".
1) Refresh inputs are ON/OFF data read from the input module using the
refresh mode.
CPU module
Input refresh area
0
X10
ON/OFF
data
These inputs are indicated as "X " in the sequence program. For
example, a "10" input becomes "X10".
2) Direct access inputs are ON/OFF data read from the input module
using the direct mode.
CPU module
Input refresh area
0
DX10
These inputs are indicated as "DX " in the sequence program.
For example, a "10" input becomes "DX10".
Direct access input can be made in a LD/AND/OR instruction that uses
an input in units of 1 point.
(b) Differences between refresh input and direct access input
Since the direct access input accesses the input module directly at
instruction execution, it imports an input faster than the refresh input.
However, the direct access input takes longer instruction processing time
than the refresh input.
Moreover, direct access inputs can only be used for inputs used with the
input module and intelligent/special function module which are installed at
main and extension base unit.
The refresh and direct input differences are shown in Table 10.2 below.
Table 10.2 Differences Between Refresh
Item
Input module installed at base/extension
base unit
Inputs of intelligent function module
installed at base/extension base unit
Inputs of I/O link module installed at
base/extension base unit
Inputs used at MELSECNET/H network
system or CC-Link system
REMARK
1: See Section 4.7.1 for details regarding the refresh mode.
1
Acquisition of ON/OFF data
2
Acquisition of ON/OFF data
Refresh Input
Usable
Usable
MELSEC-Q
Input module
Input module
Direct Access Inputs
Usable
Unusable
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