IAI America XSEL-KX - Manual (Page 80)

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Part 3 Controller Data Structure
3. Command Part
The primary feature of SEL language is its very simple command structure. Since the structure is simple,
there is no need for a compiler (to translate into computer language) and high-speed operation is possible
via an interpreter (the program runs as commands are translated).
3.1 SEL language Structure
The table below shows the structure of one command step.
Extension condition
(AND, OR)
Input condition
(I/O, flag)
Command, declaration
Output
(Output port, flag)
Command,
declaration
Operand 1 Operand 2
E N CND Pst
Using a ladder diagram, this is expressed as follows:
(1) The condition before the command is equivalent to “IF ~ THEN…” in BASIC.
[1] If the input condition is satisfied, the command will be executed. If there is an output specification, the
specified output port will be turned ON. If the input condition is not satisfied, the program will proceed
to the next step regardless of the command that follows (e.g., WTON, WTOF). Obviously nothing will
happen at the output port, but caution must be exercised.
[2] If no condition is set, the command will be executed unconditionally.
[3] To use the condition in reverse logic (so-called “contact b logic” ), add "N" (NOT) to the condition.
[4] The input condition supports input port, output port and flag.
[5] The operand 1, operand 2 and output fields can be specified indirectly.
(2) The output field, which follows the command, operand 1 and operand 2 fields, will specify the
following action:
[1] In the case of a control command relating to actuator operation, etc., the output will turn OFF the
moment the execution of command is started, and turn ON when the execution is completed. In the
case of a calculation operation command, etc., the output will turn ON if the result corresponds to a
certain value, and turn OFF if not.
[2] The output field supports output port and flag.
To the next step
Command Operand 1 Operand 2 Output
Command Operand 1 Operand 2 Output
IF ~ THEN ELSE
↓
Command Operand 1 Operand 2 Output