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MELSEC-A
2 SYSTEM CONFIGURATION
2.4.3 Precautions for using 3-axis module
When configuring a positioning system using a 3-axis module (A1SD75M3,
AD75M3), the following precautions must be observed.
(1) No. of FROM/TO commands executed in one scan
(Refer to section "6.1 Precautions for creating program" for details.)
The No. of FROM/TO commands (during 16-bit transmission), DFRO/DTO
commands (during 32-bit transmission) and special function module device
(U
\G ) executed in one scan will be as follows.
•
When carrying out circular interpolation control or S-pattern
acceleration/deceleration: 4 times/axis
•
When CHG signal is simultaneously input for two axes with speed/position
changeover control: 4 times/axis
•
Control other than the above: 10 times/axis
(2) Execution of speed/position changeover control
If there is a timing at which the CHG signal is input simultaneously for 3 axes
with the speed/position changeover control, split the AD75. (Example: Split
into 1-axis and 2-axis.)
Furthermore, machine vibration could occur because of the speed fluctuation.
2.4.4 Precautions for configuring absolute position detection system
There are the following precautions for configuring an absolute position detection
system.
•
Infinite length feed control, e.g. control in the given direction only, is not allowed.
•
Restrictions on the usable ranges of the movement amount, etc. according to the
zero point address and feedback pulse count.
Refer to section "12.6 Absolute position restoration function" for details.
2.4.5 Precautions for machine zero point return control in absolute position detection system
When machine zero point return control is executed in the absolute position
detection system, access is made to the FeRAM (Ferroelectric Random Access
Memory). (Refer to section 12.6.)
(The FeRAM is a memory capable of fast read and write and non-volatile storage,
i.e. data are not lost when power is switched off. Further it is operable at low
voltage and features that a rewritable count is more than several orders of
magnitude greater than those of the flash ROM and E
2
PROM.)
The FeRAM access count is maximum 9.9999
10
9
times.
When the FeRAM access count exceeds 9.9999
10
9
times, the absolute position
(zero point position) cannot be restored normally at a system startup (power on,
reset, etc.).
(Refer to "Appendix 4" for the zero point position storage destination and access
count for the absolute position detection system, which change depending on the
module version.)
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