I have a system where a small stepper motor is driven by an 8051-based micro through a STMicroelectronics L6219 stepper motor driver chip. The first table below shows how to sequence the L6219's control lines to run the motor in full step mode at 100% current. The second table gives the sequence for half step mode with 67% current.

 
    Full stepping with 100% current
    -------------------------------
    I02 I12 | PH2 PH1 I11 I01
    -------------------------
     0   0  |  0   0   0   0 
     0   0  |  0   1   0   0 
     0   0  |  1   1   0   0 
     0   0  |  1   0   0   0 
    
    Half stepping with 67% current
    ------------------------------
    I02 I12 | PH2 PH1 I11 I01
    -------------------------
     1   0  |  1   0   1   1 
     1   0  |  1   1   0   1 
     1   1  |  1   1   0   1 
     1   0  |  0   1   0   1 
     1   0  |  0   1   1   1 
     1   0  |  0   0   0   1 
     1   1  |  0   0   0   1 
     1   0  |  1   0   0   1 
 

These tables were derived directly from Figure 5 of the L6219 data sheet. So far, so good. No magic.

Now, based on indirect hints that I have seen here and there online, I think that it's also possible to use this chip to do quarter-stepping without any extra hardware. But I haven't found any reference that comes right out and tells directly how to do it. Does anybody here know if this is possible? If so, can you supply a control sequence to make it happen, similar to the tables given above?

Thanks,

-- Russ