MC_DigitalCamSwitch

Function block		MC_DigitalCamSwitch
Uses an axis' position to control a switch that triggers a digital output. When an axis reaches a certain position, a switch is turned on or off. A switch can be controlled by a forward and backward movement of an axis.
VAR_IN_OUT
B	AxisIn	AXIS_REF	Reference to an axis.
B	SwitchesIn	ARRAY [0..255] OF MC_CAMSWITCH_REF	Controls the switching actions. The track numbers need to be in order.
E	OutputsIn	ARRAY [0..31] OF MC_OUTPUT_REF	Selects which digital output will be controlled by the corresponding track.
E	TracksIn	ARRAY [0..31] OF MC_TRACK_REF	Adds the compensation time and hysteresis to the switches on a track. The TrackNumber is defined in Switches.
VAR_INPUT
B	Enable	BOOL	Enables the tracks. If this value is FALSE, all tracks are disabled; if this is TRUE, see EnableMask to check if the specified tracks are enabled.
E	EnableMask	DWORD	Enables the different tracks. This parameter is 32 bits of BOOL. The corresponding track in the track array is enabled when its BOOL value is set to one.
E	ValueSource	MC_Source	Defines the source for axis values. For example, positions: mcCommandedValue, mcSetValue – synchronization on set value. We suggest you use these settings. mcActualValue – synchronization on actual value. This setting may not be stable.
VAR_OUTPUT
B	InOperation	BOOL	Checks whether the commanded tracks are enabled.
E	Busy	BOOL	The function block is not finished and new output values are to be expected.
B	Error	BOOL	Signals that an error has occurred within the function block.
E	ErrorID	MC_Error	Error identification.
MC_CAMSWITCH_REF is a vendor specific structure that defines switches for digital cam. MC_OUTPUT_REF is a vendor specific structure linked to the (physical) outputs. MC_TRACK_REF is vendor specific structure containing the track properties. For example, the compensation per track (A track is a set of switches related to one output). It can also contain the reference to the output. This functionality is sometimes called PLS – Phase or Position or Programmable Limit Switch.

	MC_DigitalCamSwitch
AXIS_REF	AxisIn	Axis	AXIS_REF
ARRAY [0..255] OF MC_CAMSWITCH_REF	SwitchesIn	Switches	ARRAY [0..255] OF MC_CAMSWITCH_REF
ARRAY [0..31] OF MC_OUTPUT_REF	OutputsIn	Outputs	ARRAY [0..31] OF MC_OUTPUT_REF
ARRAY [0..31] OF MC_TRACK_REF	TracksIn	Tracks	ARRAY [0..31] OF MC_TRACK_REF
BOOL	Enable	InOperation	BOOL
DWORD	EnableMask	Busy	BOOL
MC_Source	ValueSource	Error	BOOL
		ErrorID	MC_Error

Elements within the MC_CAMSWITCH_REF structure

B/E	Parameter	Type	Description
B	TrackNumber	INT	The index of a track. Indexes are zero-based.
B	FirstOnPosition [user unit]	LREAL	The position from which the switch is on.
B	LastOnPosition [user unit]	LREAL	The position from which the switch is off.
E	AxisDirection	INT	The direction of an axis. The default value is zero. If you select one or two, the switch is active only when the axis is moving in the specified direction. Both: 0, Positive: 1, Negative: 2.
E	CamSwitchMode	INT	The cam switch is controlled by axis' positions or time. The default value is zero. If choosing Position, you need to set FirstOnPosition and LastOnPosition; if choosing Time, you need to set FirstOnPosition and Duration. Position: 0, Time: 1.
E	Duration	TIME	How long the switch is on. This property is available when CamSwitchMode is Time. The unit is second.

Elements within the MC_TRACK_REF structure

B/E	Parameter	Type	Description
E	OnCompensation	TIME	The length of time with which a switch is turned on (rising edge) before or after a switching point per track. If the value is positive, the switch-on will be delayed; if the value is negative, the switch-on will be advanced.
E	OffCompensation	TIME	The length of time with which a switch is turned off (falling edge) before or after a switching point per track. If the value is positive, the switch-off will be delayed; if the value is negative, the switch-off will be advanced.
E	Hysteresis [unit]	LREAL	The distance from a switching point (in positive and negative direction) in which a switch is not turned on or off until the axis has left this area. This can avoid frequent switching around a switching point.

This definition of a cam has a start and an end position, so the user can define each single cam, which has a FirstOnPosition and a LastOnPosition (or time). This function or function block is similar to a mechanical cam but has the additional advantages that the outputs can be set for a certain time, and to give it a time-compensation and a hysteresis.

CamSwitchMode: it can be position or time.

Duration: time, the output of a time cam is ON. The time compensation (OnCompensation and OffCompensation) can be positive or negative. Negative means the output changes before the switching position is reached.

Hysteresis: this parameter avoids the phenomenon where the output continually switches if the axis is near the switching point and the actual position is jittering around the switching position. Hysteresis is part of MC_TRACK_REF, which means that a different hysteresis is possible for each track.

Example of MC_CAMSWITCH_REF

Parameter	Type	Switch01	Switch02	Switch03	Switch04
TrackNumber	INTEGER	1	1	1	2
FirstOnPosition [unit]	LREAL	2000	2500	4000	3000
LastOnPosition [unit]	LREAL	3000	3000	6000	--
AxisDirection	INTEGER	1=Pos	2=Neg	0=Both	0=Both
CamSwitchMode	INTEGER	0=Position	0=Position	0=Position	1=Time
Duration	LREAL	--	--	--	1.35 seconds

Example of MC_OUTPUT_REF

Parameter	MC_OUTPUT_REF[0]	MC_OUTPUT_REF[1]	MC_OUTPUT_REF[2]	-	-	-	MC_OUTPUT_REF[31]
IsAxis	FALSE	FALSE	FALSE	-	-	-	FALSE
Index	0	0	0	-	-	-	0
BitOffset	0	1	2	-	-	-	31

Example of an I/O module

The figure below uses the values from the example of MC_CAMSWITCH_REF above. It uses neither On/OffCompensation nor Hysteresis. This is the behavior of the outputs, when the axis is moving continuously in the positive direction.

MC_DigitalCamSwitch – Positive Direction

Positive Direction: Behavior of the Outputs

TrackNumber 1 (Switch01, 02, 03) is mapped to MC_OUTPUT_REF[1] and TrackNumber 2 (Switch04) is mapped to MC_OUTPUT_REF[2]. When Switch01, Switch02, and Switch03 are triggered, the second output (Output 1) on the first I/O module (Index 0) is turned on. When Switch04 is triggered, the third output is turned on (Output 2).

Example of On/Off Compensation

This example uses OnCompensation -125ms and OffCompensation +250ms.

The figure below shows the behavior of the outputs, when the axis is moving continuously in the negative direction without On/OffCompensation and Hysteresis.

MC_DigitalCamSwitch – Negative Direction

Negative Direction: Behavior of the Outputs

EnableMask

EnableMask is a DWORD parameter that contains 32 bits. Each bit is a BOOL value that controls an output. An output is enabled or disabled by setting its corresponding bit TRUE or FALSE. For example, bit 0 controls MC_OUTPUT_REF[0] and bit 1 controls MC_OUTPUT_REF[1]. If bit 0 and 1 are TRUE, their outputs are enabled, which means their outputs will be turned on when their corresponding switches are triggered; if they are FALSE, their outputs are disabled, which means their outputs won't be turned on even if their corresponding switches are triggered.

Bits	Bit 0	Bit 1	Bit 2	Bit 3	-	-	-	-	Bit 31
Value	TRUE/FALSE	TRUE/FALSE	TRUE/FALSE	TRUE/FALSE	-	-	-	-	TRUE/FALSE

Example of MC_OUTPUT_REF

Parameter	MC_OUTPUT_REF[0]	MC_OUTPUT_REF[1]	MC_OUTPUT_REF[2]	-	-	-	MC_OUTPUT_REF[31]
IsAxis	FALSE	FALSE	FALSE	-	-	-	FALSE
Index	0	0	0	-	-	-	0
BitOffset	0	1	2	-	-	-	31

Example 1 of EnableMask Bits

Bit 0, 1, and 2 are TRUE, which means Output 0, 1, and 2 are enabled. The outputs are turned on when their corresponding switches are triggered.

Bits	Bit 0	Bit 1	Bit 2	Bit 3	-	-	-	-	Bit 31
Value	TRUE	TRUE	TRUE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE

Positive Direction: Behavior of the Outputs

Example 2 of EnableMask Bits

Bit 0 and 2 are TRUE, which means Output 0 and 2 are enabled. Only these two outputs are turned on when their corresponding switches are triggered.

Bits	Bit 0	Bit 1	Bit 2	Bit 3	-	-	-	-	Bit 31
Value	TRUE	FALSE	TRUE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE

Positive Direction: Behavior of the Outputs

Example 3 of EnableMask Bits

All bits are FALSE, which means all outputs are disabled. No outputs are turned on even if their corresponding switches are triggered.

Bits	Bit 0	Bit 1	Bit 2	Bit 3	-	-	-	-	Bit 31
Value	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE

Positive Direction: Behavior of the Outputs