Mitsubishi L02CPU User Manual page 260

(b) When "High Speed Execution" is selected
1) The CPU module does not save index register
values at program switching.
Execution program
Index register value
Save area of index register
for scan execution
type program
*1 The Z0 value is changed to 3 in the interrupt program.
When writing data to the index register, use the ZPUSH or ZPOP instruction to save and restore the data. (
Q/L Programming Manual (Common Instruction))
(3) Processing of file register block numbers
1) The CPU module saves the block numbers of
the file register and passes them at program
switching.
Execution program
Block No. of
file register
Save area
258
2) If data are written to the index register, the values of
the index register used in the scan execution type program
will be corrupted at program switching.
Scan execution
type program
Z0 = 1
Z0 = 0
Switching
Scan execution
type program
Passed
Block 1
Saved
Block 0 Block 1
Interrupt/fixed
Switching Restored
scan execution
type program
Passed Passed
Z0 = 1 Z0 = 3
* 1
Z0 = 0 Z0 = 0
2) The CPU module restores the block
Interrupt/fixed
Restored
scan execution
type program
[RSET K0]
Block 1 0
Block 1 Block 1
3) The index register
values are not saved.
Scan execution
type program
Z0 = 3
Z0 = 0 Z0 = 0
numbers of the file register saved at
program switching.
Scan execution
type program
Block 1
Restored
Block 1
MELSEC-