Index Setting - Mitsubishi Electric MELSEC Q Series Structured Programming Manual

4.6

Index Setting

(1) Overview of the index setting
(a) The index setting is an indirect setting that uses index registers.
When the index setting is used in a sequence program, the device consists of 'directly
specified device number' + 'content of index register'.
For example, when D2Z2 is specified and the value of Z2 is 3, D(2+3)=D5 is set as the
target.
(b) For Universal model QCPU, LCPU, and FXCPU, indexes can be set in 32-bit range in
addition to 16-bit range.
(2) 16-bit index setting
(a) Setting an index in 16-bit range
Values from -32768 to 32767 can be set to index registers
The following shows how the index is set.
X0
-1
X0
D10Z0
*1 For the index setting, refer to the user's manual (function explanation, program
fundamentals) for the CPU module used.
(b) Devices that can be used for the index setting (for QCPU (Q mode), LCPU)
The index setting can be applied to devices used by contacts, coils, basic instructions,
and application instructions except for the restrictions listed in the tables below. The
index setting cannot be applied to labels.
1) Devices that cannot be used for the index setting
Device
E
$
. (D0.1 etc.)
FX, FY, FD
P
I
Z
S
TR
BL
*2: SFC transition devices and SFC block devices are devices
for SFC programs. For details, refer to the following manual.
• MELSEC-Q/L/QnA Programming Manual (SFC)
*3: The SFC block devices (BL) and step relays (S) of a High-speed Universal model QCPU can be used for
the index setting under the following ranges.
• SFC block device (BL): BL0 to BL319
• Step relay (S): Within the range set in the parameter
When the step relays (S) in an SFC block device are selected, S0 to S511 can be used for the index
setting.
MOV
Stores -1 at Z0.
EN ENO
s d Z0
MOV
Stores the data of D10Z0=
EN ENO
D{10+(-1)} = D9 to D0.
s d D0

Index setting

Description
Floating-point data
Character string data
Bit-specified word device
Function devices
Pointers used as labels
Interrupt pointers used as labels
Index registers
*3
Step relays
SFC transition devices
*3
SFC block devices
*1
.
*2
4.6 Index Setting
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