Yaskawa YASNAC PC NC PLC Programming Manual - Manual (Page 20)

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YASNAC PCNC PLC Programming Manual Chapter 4: Sequence Control Method
4.2 Operation of Sequence Program
4.2.1 Sequence Program
Length of time necessary for the execution of one cycle of a sequence program is called the scan
time. The scan time of this model of PLC is indicated below.
• High-speed processing scan time: 8 msec
• Low-speed processing scan time: 8 msec × n
This means, with this PLC, the sequence program can be processed by dividing it into a high
speed processing part and low-speed processing part. Therefore, the sequence program must be
written in the format indicated below.
Fig. 4.2 Sequence Program Format
As indicated above, the sequence program that requires high-speed processing should be entered
first and the sequence program for which low-speed processing is acceptable should be entered
after that.
4.2.2 Operation
The operation time chart of PCNC sequence program is indicated below.
Fig. 4.3 PCNC Operation Time Chart