Mitsubishi Electric MELSEC iQ-R Series - Page 129

8 RUNNING A PROGRAM
8.7 Interrupt Program
127
8
Saving/restoring of the index register (Z, LZ)
When an interrupt program starts, the value of the index register (Z, LZ) of the running program is saved. When the interrupt
program finishes, and the saved value is restored to the running program. Note that when an interrupt program starts, the
local index register (Z, LZ) is not switched to the different one. When the local index register (Z, LZ) is used for the interrupt
program/fixed scan execution type program/event execution type program which uses occurrence of an interrupt as a trigger,
the register which has been used for the previous program is continuously used. Thus, the local index register (Z, LZ) cannot
be used independently.
• Saving/restoring of the index register
• Operations of the local index register and local device
*1 The value of Z0 is changed by the interrupt program, fixed scan execution type program, or event execution type program.
*2 For when SM777 is on (when using the local device of the program file of storage location)
(1) This value can be used as a value specific to the scan execution type program. (Using the value in an interrupt program is not needed to be concerned.)
(2) This value can be used only at the moment an interrupt program, fixed scan execution type program, or event execution type program is executed. (The
value cannot be used continuously.)
Z0=0 Z0=3
*1
Z0=0
Z0=0
Z0=0
Z0=0
Z0=0
Z0=0
(2)
(1)
Interrupt program/
Fixed scan execution type program/
Event execution type program
Execution program
Value of the index register
Scan execution
type program
Switch
Scan execution
type program
Switch
Save
Return
Save area of the index
register
(for scan execution type
programs)
Interrupt program/
Fixed scan execution type program/
Event execution type program
Without change
Save
Return
Without change
Z0=0→Z0=1 Z0=1→Z0=10 Z0=1Z0=1
#D0=0→#D0=1 #D0=1
#D0=0→#D0=100 #D0=100
Execution program
Local index register (Z0) for A
Local index register (Z0) for B
Local device (#D0) for A
*2
Local device (#D0) for B
*2
Scan execution
type program (A)
Scan execution
type program (A)
Switch Return
Return
Switch
Save Save
Not used Not used
Interrupt program/
Fixed scan execution type program/
Event execution type program (B)
Interrupt program/
Fixed scan execution type program/
Event execution type program (B)
Without change Without change