<8. Detailed Description>
8.4.4 Selecting between SFC and Stepped FBD or LD
● Characteristics of SFC Programming Language
The SFC is a step execution type of language, which processes one step after
another, and is thus ideal for building process progress type applications and
sequence control applications. The figure below shows a schematic of an SFC
application.
STEP0
STEP1
ACTION1
STEP2
ACTION2
STEP3
ACTION3
TRANSITION1
TRANSITION2
TRANSITION3
TRANSITION4
In the application shown in the above picture, while the SFC process is at initial step
STEP0 and the process transition condition TRANSITION1 becomes true, the
process moves to STEP1 and ACTION1 is executed.
While the process is at STEP1 and TRANSITION2 becomes true, the process
moves to STEP2 and ACTION3 is executed.
Similarly, while the process is at STEP2 and TRANSITION3 becomes true, the
process moves to STEP3 and ACTION3 is executed.
While the process is at STEP3 and TRANSITION4 becomes true, the process
moves to initial step STEP0.
In this way, processing in SFC progresses one step at a time so SFC is well suited
for building process progress type applications and sequence control applications.
Moreover, actions of ACTION 1, ACTION 2 and ACTION3 can be coded in FBD, LD,
IL or ST language.
For ease of explanation, a simple description of actions of ACTION1, ACTION2 and
ACTION3 is shown in the above figure; the actual operation of SFC is a little more
complex.
For details, see Logic Designer’s online help documentation.
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