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MELSEC-Q
10 DEVICES
10.6.1 Switching between scan execution type programs and low speed execution type
programs
When switching from a scan execution type programs or low speed execution type
program to another program type, the index register (Z0 to Z15) data is saved
(protected) and reset.
(1) Index register processing at switching between scan execution type
programs and low speed execution type programs
(a) When switching from a scan execution type program to a low speed
execution type program occurs, the scan execution type program's index
register data is saved, and the low speed execution type program's index
register data is restored.
(b) When switching from a low speed execution program to a scan execution
type program occurs, the low speed execution type program's index
register data is saved, and the scan execution type program's index register
data is restored.
Executed program
Index register value
Index register
storage area
Scan execution
type program
Switch-
ing
Z0=1
Low speed
execution
type program
Z0=3
Z0=0
Z0=0
Z0=1
Z0=0
Z0=1
Z0=0
Z0=1
Z0=3
Z0=1
Z0=3
Z0=6
Z0=3
Z0=6
Z0=3
Saved
Reset
Saved Reset
Saved
Reset
Z0=0 to Z0=3
1
1: For low-speed execution type program, Z0 is changed to 3.
2: For scan execution type program, Z0 is changed to 6.
Z0=1 to Z0=6
2
For low speed
execution type
program
For scan execution
type programs
Scan execution
type program
Low speed
execution
type program
Switch-
ing
Switch-
ing
(2) Exchanges of index register data
Word devices should be used for exchanges of index register data between scan
execution type programs and low speed execution type programs.