
4. AnSHCPU MODULE
4 - 3
MELSEC-A
4.1.1
Outline of AnSHCPU operation processing
This section explains the operation processing which takes place from the time the
AnSHCPU power is switched ON until the sequence program is executed.
AnSHCPU processing is generally divided into the following four types:
(1)
Initial processing
This is the pre-processing for executing sequence operations. Initial
processing is executed once at power up or after key reset.
(a)
Resetting the I/O module.
(b)
Initialization of the data memory's unset latch area (bit devices turned
OFF, word devices set to 0).
(c)
I/O module addresses are automatically assigned in accordance with the
I/O module type and where the module is installed on a base unit.
(d)
Automatic diagnostic check of parameter settings and operation circuits
is executed (see Section 4.1.6).
(e)
If the AnSHCPU is used in the master station of an MELSECNET(II)
MELSECNET/B, data link operation begins after setting the link
parameter data in the data link module.
(2)
I/O module refresh processing
If the refresh mode for both input and output is set with the I/O control switch,
the I/O module is refreshed (see Section 4.1.5).
(3)
Sequence program operation processing
The sequence program written in the AnSHCPU is executed from step 0 to
the END instruction.
(4)
END processing
When sequence program processing reaches the END instruction, the
sequence program is returned to step 0.
(a)
Self-diagnosis checks for blown fuses, I/O module verification, low
battery voltage, etc., are executed (see Section 4.1.6).
(b)
T/C present values are updated and contacts are turned ON/OFF. (The
ACPU Programming Manual (Fundmentals) gives details.)
(c)
Data read or write from/to computer link modules (A1SJ71UC24-R2,
etc.)
(d)
Link refresh processing is executed when the link refresh request is
given from the MELSECNET data link.
Note that the AnSHCPU can enable and disable execution of link refresh
by turning M9053 ON/OFF and by issuing DI/EI instructions.
(e)
When sampling trace is performed for every scan (after an END
instruction is executed), the status of the set device is stored in the
sampling trace area.
Содержание A1SH
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