1. SPiiPlus Training Class
PEG and MARK

2. What is PEG?
PEG (Position Event Generator) creates pulses based on exact feedback position. These events can be used as a trigger for external devices, such as a camera, laser, etc.
A PEG pulse is generated in hardware (delay < 0.1 microsecond) by comparing actual encoder position with a set of predefined values
Two different PEG modes:
Incremental PEG:
Pulse at fixed position increments
Random PEG:
Pulse at user-defined positions
Update a 4-bit state vector at each position

3. What is PEG?
PEG accuracy: ±1 count up to 10M counts/sec (using a digital encoder)
Three PEG engines per SPii
PEG engine outputs can be assigned to 10 physical RS422 interface outputs
PEG pulses can be sent in parallel through opto-isolated general purpose digital outputs, along with physical PEG outputs
PEG pulse width and polarity are programmable
Physical PEG outputs can be configured as RS422 general purpose outputs

4. Incremental PEG Mode
A pulse is generated at a predetermined start position followed by a stream of pulses a fixed distance apart until a predetermined end position is reached

5. Incremental PEG Mode
Maximum Incremental PEG pulse output frequency is 18 MHz.
Maximum Incremental PEG edge separation is (1/18MHz) = nSec.
Pulse width range is nSec to mSec.
Direction of motion should correspond to sign of Interval.

6. How to use Incremental PEG
Use ASSIGNPEG to define which encoder PEG will use
Use ASSIGNPOUTS to define physical output pins PEG will use
Use PEG_I to set Incremental PEG
Wait for PEGREADY
Command motion to fire PEG pulses
(Optional) use STOPPEG to end PEG process before completion

7. ASSIGNPEG The ASSIGNPEG command is used for:
Defining which encoders PEG will use
Configuration of digital outputs (for optional use as PEG signals)
A single ASSIGNPEG command effects all three PEG engines and all four general purpose outputs on a servo processor
ASSIGNPEG axis, engines_to_encoders_code, gp_out_assign_code
axis: Used to identify the relevant servo processor
engines_to_encoders_code: Bit code for engines-to-encoders mapping
gp_out_assign_code: General purpose outputs assignment to use as PEG state and PEG pulse outputs
For relevant bit codes, refer to SPiiPlus NT PEG and MARK User Guide

8. ASSIGNPEG Example 1 ASSIGNPEG 0, 0b000, 0b0000
0: Assign all three PEG engines on servo processor 0
0b000: The following assignments are all made:
PEG engine 0 assigned to encoder 0
PEG engine 1 assigned to encoder 1
PEG engine 2 assigned to encoder 2
0b0000: The following assignments are all made:
General purpose output 0 configured as general purpose output 0
General purpose output 1 configured as general purpose output 1
General purpose output 2 configured as general purpose output 2
General purpose output 3 configured as general purpose output 3

9. ASSIGNPEG Example 2 ASSIGNPEG 5, 0b010, 0b0110
5: Assign all PEG engines on servo processor 1
0b010: The following assignments are all made:
PEG engine 4 assigned to encoder 4
PEG engine 6 assigned to encoder 4
PEG engine 5 assigned to encoder 5
0b0110: The following assignments are all made:
General purpose output 4 configured as PEG_Pulse(4)
General purpose output 5 configured as general purpose output 5
General purpose output 6 configured as PEG_Pulse(5)
General purpose output 7 configured as general purpose output 7

10. ASSIGNPOUTS
Physical PEG pins can be used for either PEG (default) or as additional general purpose outputs. The ASSIGNPOUTS command is used to configure these pins accordingly.
ASSIGNPOUTS axis, output_index, bit_code
axis: Used to identify the relevant servo processor
output_index: 0 for X_PEG pins, 1 for Y_PEG pins, etc.
bit_code: Bit code for pin designation as PEG or as general purpose
For relevant bit codes, refer to SPiiPlus NT PEG and MARK User Guide

11. ASSIGNPOUTS Examples ASSIGNPOUTS 3, 1, 0b000 ASSIGNPOUTS 4, 5, 0b111
3: Pins corresponding to servo processor 0
1: Y_PEG pins to be assigned
0b000: Send PEG1_Pulse through Y_PEG pins
ASSIGNPOUTS 4, 5, 0b111
4: Pins corresponding to servo processor 1
5: X_STATE0 pins to be assigned
0b111: X_STATE0 set as general purpose out (OUT(1).20)
ASSIGNPOUTS 4, 5, 0b010
0b010: PEG4_Pulse sent through X_STATE0 output

12. Incremental PEG PEG_I Axis, Width, First Point, Interval, Last Point
Encoder PEG is based on
Width
Pulse width (ms). Range is 26.67ns to 1.745ms
First Point
Position of first pulse in user units
Interval
Distance between pulse points in user units
Last Point
Position for last pulse in user units

13. Incremental PEG
PEG_I X, 0.003, 1000, 1000, 3000

14. AST.#PEGREADY
AST is an integer array containing a set of bits used for displaying the current axis state
Bit 4 (#PEGREADY) indicates the readiness of a PEG engine
Syntax: AST(axis).#PEGREADY
Make sure this bit = 1 before commanding motion of the PEG axis

15. STOPPEG and STARTPEG
STOPPEG axis terminates PEG on the specified axis. The command is used in both Incremental and Random PEG.
Useful for safety purposes to stop PEG pulses while axis is in motion
If STOPPEG has been executed before the last PEG point has been reached, STARTPEG can be used to continue PEG from the current position.
STARTPEG axis command initiates the PEG process on the specified axis. The command is used in both the Incremental and Random PEG modes.

16. MARK
MARK (position registration) provides ability to latch current axis position when digital input signal is received
In many applications such as packing, it is desired to move an axis to a target that is relative to a registration mark
Once an axis is moving and a MARK is detected, motion profile can be modified on-the-fly to reach new target position

17. MARK ACSPL+ variable MARK(axis) stores last MARK position
MARK inputs can be assigned as fast general purpose inputs using the ASSIGNFINS command
Maximum MARK input frequency depends on CTIME and other factors, and ranges between 50Hz for CTIME = 1ms, and 100Hz for CTIME = 0.5ms
MARK inputs are routed according to ACSPL+ variables SLPROUT, SLVROUT, SLCROUT. Routing two axes to a single input will cause undefined MARK behavior and should be avoided

18. Feedback Routing
SLPROUT is used for routing feedback position for the specified axis
SLVROUT is used for routing feedback velocity for the specified axis
SLCROUT is used for setting the feedback routing of the commutation velocity for the specified axis
Syntax: SLPROUT(AXIS#) = value, SLVROUT(AXIS#) = value, SLCROUT(AXIS#) = value
Where value corresponds to feedback source (see tables 34, 35, and 36 of the SPiiPlus ACSPL+ Command & Variable Reference Guide for definition)

19. ASSIGNFINS
ASSIGNFINS can be used to set MARK inputs as fast general purpose inputs
ASSIGNFINS axis, output_index, bit_code
axis: Used to identify the relevant servo processor the axis is controlled by
input_index: 0 for IN_0, 1 for IN_1, ..., 9 for IN_9
bit_code: Bit code for mapping MARK inputs to physical inputs
For relevant bit codes, refer to SPiiPlus NT PEG and MARK Operations tables 11 and 12

20. ASSIGNFINS Examples ASSIGNFINS 1, 1, 0b111
1: Servo processor 0 is being used
1: MARK Y input
0b111: MARK Y set to FGP_IN1
FGP_IN1 associated ACSPL+ variable: IN(0).17
ASSIGNFINS 4, 5, 0b111
4: Servo processor 1 is being used
5: MARK T input
0b111: MARK T set to FGP_IN3
FGP_IN3 associated ACSPL+ variable: IN(1).19

21. MARK Example Assume the following motion should be built:
Move axis at a constant velocity with no defined end point
Latch exact MARK position while moving
Redefine the end point on the fly and stop motion smoothly at position equal to mark position plus units
IST(0).#MARK = ! Enable MARK latching
JOG ! Jog in positive direction
TILL IST(0).#MARK ! Wait for MARK signal
PTP 0, MARK(0) ! Move to MARK(0)

22. Using PEG and MARK with SIN-COS Encoder
When SIN-COS encoder is used PEG and MARK can only be fired/captured at zero-crossings of the sine/cosine waves (not at the exact interpolated position)

23. GETCONF GETCONF retrieves system configuration data
GETCONF(71, index): Use to view the actual assignment of digital outputs to PEG states and PEG pulses outputs. Index argument contains the axis index.
GETCONF(72, index): Use to view the actual encoder PEG engine assignment. Index argument contains the axis index.
GETCONF(73, index): Use to view the actual output pins assignment. Index argument: 0-7 is axis index, 8-16 is OUT_0 through OUT_9

24. Further Information
The following guides are part of the SPiiPlus NT Suite installation:
PEG and MARK Application Notes
ACSPL+ Command and Variable Reference Guide
SPiiPlus ACSPL+ Programmer’s Guide

25. Example 1
A non-destructive testing machine requires RS422 PEG pulses be sent to its ellipsometry system for triggering purposes during stage travel.
Triggering needs to occur at fixed intervals along the stage’s length of travel
The application is using a CMnt
Method:
Load and review example code

26. Example 2
The inspection machine just had a HW revision, and now requires two metrology systems to be triggered in parallel.
Being a cost sensitive application it is desired to do this without adding/designing/purchasing/testing external circuitry.
Method:
Modify code in previous example so two RS422 PEG pulses are sent out in parallel instead of one

27. Example 3
For qualification purposes it needs to be verified that pulses are being fired at correct positions.
Method:
Physically connect PEG pins to MARK pins
Modify the previous example to display MARK positions in the Communication Terminal
Hint – use an autoroutine to
Detect MARK latching (IST(axis).#MARK = 1)
Display the latched position (MARK(axis))
Reset latch (IST(axis).#MARK = 0) so next PEG pulse can be detected