Index Setting - Mitsubishi Electric MELSEC Q Series Programming Manual

4.6

Index Setting

Overview of the index setting
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.
For Universal model QCPU, LCPU, and FXCPU, indexes can be set in 32-bit range in addition to 16-bit range.
16-bit index setting
■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
MOV
EN ENO
-1 s d
X0
MOV
EN ENO
D10Z0
s d
Index setting
*1 For the specifications of the index register, refer to the User's Manual (Function Explanation, Program Fundamentals) for the CPU
module used.
■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.
• Devices that cannot be used for the index setting
Device
E
$
. (D0.1 etc.)
FX, FY, FD
P
I
Z
S
TR
BL
*1 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)
*2 The SFC block devices (BL) and step relays (S) of the High-speed Universal model QCPU and Universal model Process CPU can be
used for the index modification under the following ranges.
 SFC block device (BL): BL0 to BL319
 Step relay (S): Within the range set in the parameter (device settings)
When the step relays (S) in an SFC block device are selected, S0 to S511 can be used for the index setting.
*1
Stores -1 at Z0.
Z0
Stores the data of D10Z0=
D{10+(-1)} = D9 to D0.
D0
Description
Floating-point data
Character string data
Bit-specified word device
Function devices
Pointers used as labels
Interrupt pointers used as labels
Index registers
*2
Step relays
SFC transition devices
*1*2
SFC block devices
*1
4 PROGRAM CONFIGURATION
4
57
4.6 Index Setting