There's a great read here at this link:
http://www.stepperworld.com/pgTutorials.htmNote in both the unipolar and bipolar links where he states
"In a basic "Wave Drive" clockwise sequence, winding 1 is de-activated and winding 2 activated to advance to
the next phase. The rotor is guided in this manner from one winding to the next, producing a continuous cycle.
Note that if two adjacent windings are activated, the rotor is attracted mid-way between the two windings.
The following table describes 3 useful stepping sequences and their relative merits. The polarity of terminals is
indicated with +/-. After the last step in each sequence the sequence repeats. Stepping backwards through the
sequence reverses the direction of the motor. Note that these sequences are identical to those for a Unipolar
Stepper Motor.
As you can see on the top scope (the one that shows the xy plot) the waveforms maintain a constant phase angle during a stop. Please note that the scope is showing the input to the gates of the drive MOSFETs. If you look at the schematic on the yahoo maxnc site - I have a copy of it on my site here:
http://home.comcast.net/~ajawam5/max/Cirquit_diagram-Maxnc15CL-Controller.pdfthat otto simply made his software on the PC output a quad signal on two pins to the PIC microcontrollers. So instead of having to generate the drive signal for the FETS/Darlington transistors (depends on the model MAXNC Controller) from a step and direction signal, he used the MAXNC PC software to generate the quad signal... simplifying the logic required in the maxnc controller/drive. This also allowed him a bit more latitude on being able to alter the drive timing characteristics on the PC side of things.
The old DOS MAXNC disk had a dos program called TIMESET that wrote parameters to a file to control the timing based on the PC's characteristics
This is from an email Art sent me long ago:
"Yes, when you select the CL option, which is quadrature outputs, the pin
settings you use are ignored and set as per factory specs for the CL pins.
Usually, in CL mode the user sets pin 17 as the enable output. Then it is
low until you press reset to enable the controller
at which point it goes high, this suffices to reset the CL.
The Enable pin shoudl work for that.. Also, in CL mode , the Input#1 is
normall used as a hold for position signal to
keep the CL from overruning in speed. I believe pin 10 as below is used. If
pin 10 goes active (Active high) then output stops till the Max determines
its OK for further movement. This makes the CL a semi-closed loop system.
(Hence the CL designation..) Make sure then that pin 10 is set to Input #1
and is set "High active". Setting Pin17 to Enable#1, and setting it "high
Active" as well makes the CL reset when MAch3 does. Also youll notice pin 16
below is the real enable, so you need to set Enable #2 signal to pin 16 and
set it low active" to allow movement when in CL mode.
Here are the MaxCL pinouts..
1............... M3 OUTPUT (LOW=ON, PULSE FOR PWM)
2............... A AXIS (quadrature)
3............... A AXIS (quadrature)
4............... Y AXIS (quadrature)
5............... Y AXIS (quadrature)
6................X AXIS (quadrature)
7............... X AXIS (quadrature)
8............... Z AXIS (quadrature)
9............... Z AXIS (quadrature)
10.............. INPUT, MOVE ENABLE (LOW=NORMAL OPERATION, HIGH=STOP, SEE
NOTE)
11.............. INACTIVE
12.............. INPUT, HOME SWITCH (NORMAL OPERATION LOW)
13.............. INPUT, G61 SWITCH SENSOR
14.............. M8 OUTPUT (LOW=ON)
15.............. NONE
16.............. OUTPUT, DISABLE POWER TO MOTORS (LOW=NORMAL, HIGH=DISABLE)
17.............. OUTPUT, RESET CONTROLLER (LOW=RESET, HIGH=NORMAL)
18.............. ALL SIGNALS GROUND
19 TO 25 ....... NONE
"
One of the best sites on steppers I've found is at U of Iowa:
http://homepage.cs.uiowa.edu/~jones/step/