MC-Basic:COMMON SHARED ... AS PLS

This command declares a programmable limit switch (PLS) variable. In the declaration, the name of the axis and the output associated with the PLS are specified. The PLS output pattern is generated for the position of that axis. The output associated with a PLS may be a digital output (specified using SYSTEM.DOUT.x) or a virtual output (specified using SYSTEM.VOUT.x).

After this command is processed, the following default PLS properties are in effect:

• The initial output polarity is 1.
  
• The repetition interval is set to 0.
  
• The hysteresis is set to 0.
  
• A single PLS position exists at 0

The hardware assisted PLS is proposed in order to overcome a limitation of scan time. Having current position, speed and acceleration software can predict (extrapolate) exact time when axis will reach desired position. The output operation must be performed at the extrapolated point of time.

These properties may be set explicitly when the PLS is disabled. The PLS exists, but is disabled after it is declared. The PLS property <pls>.PLSENABLE is used to enable the PLS.

Syntax

COMMON SHARED <pls>As Pls <axis> <output> {HWAssistance = TRUE/FALSE }

Availability

HWAssistance: Since Version 4.1.11 / 4.2.16  firmware with 8.7.1 Altera version

Type

<pls>:string
<axis>: string

Range

<axis>: a valid axis name
<output>: the name of a system output. System outputs are specified by

System.DOut.x, for digital outputs, or

System.VOut.x, for virtual outputs.

The hardware assisted PLS works with System.DOut from 1 to 8

<HWAssistance>: TRUE  - starts the hardware assisted PLS  mode

FALSE

The value xidentifies the specific output to be used. It may be explicitly given or it may be an expression. The expression must evaluate to an integer ranging from 1 to 20 for digital outputs or from 1 to 32 for virtual outputs.

Scope

Configuration or Terminal .

Since Version 4.5.17 the global (common shared) declaration is also possible from the Library or Task contexts. In those contexts all three parameters of PLS (axis name, system output and HWassistance flag) can be reassigned during the reloading the declaring task or library.

Limitations

Write only

HWAssistance feature works for Digital Logic Pentium III CPU  with 8.7.1 Altera version  only !

Examples

Common Shared Pls1 as PLS x_axis SYSTEM.Dout.4

Common Shared Pls2 as PLS x_axis SYS.Dout.8 HWAssistance = TRUE

Common Shared Pls3 as PLS x_axis SYS.Dout.3 HWAssistance = FALSE

See Also

• pls.PLSAXISNAME
• pls.PLSENABLE
• pls.PLSHYSTERESIS
• pls.PLSOUTPUT
• pls.PLSPOLARITY
• pls.PLSPOSITION
• pls.PLSREPEAT
• PLSLIST
• pls.HWASSISTANCE