CY545 Stepper System Controller
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Moving the Motor
Finally, two commands are used to actually make the motor move, based on the currently
defined parameters. They are:
G
Step in a relative mode
P Pos24
Step to the specified target position
The Go command selects relative mode stepping. The CY545 will step based on the last
Number of steps specified and the selected step direction. A continuous mode step motion may
also be started by this command.
Absolute mode stepping is selected by the Position command. This command both specifies
the desired target position and starts the motion. When the target is specified, the CY545 will
compute the number of steps to take and the direction of motion, based on the current position
register.
If the target position is greater than the current position, the CY545 steps in the CW direction. If
the target position is less than the current position, the CY545 steps in the CCW direction.
Recall that the current position is defined by the At command, and is updated with every motion.
It is a 24-bit value, ranging from 0 to 16777215. The Position command limits stepping to a
number of steps within this range.
Position Counter “Wrap-around”
If a relative motion causes overflow or underflow of the current position register, an absolute
move would now work within the new block of 16 million steps. For example, if the current
position is 00000020, and the following commands are executed:
N 30<cr>
-<cr>
G<cr>
The motor will step 30 steps CCW, and the current position register will underflow to a value of -
10, which is 16777205. If you now command:
P.0<cr>
The motor will step 16 million steps in the
CCW direction, since the CY545 believes
the motor is at position 16777205. It does
not remember that an underflow occurred,
and will not take 10 steps CW to get back to
the original position 0.
This behavior also allows stepping to regions beyond the 16 million step block supported by the
CY545. As long as you can work within a block of 16 million steps, relative mode stepping can
be used to move from one block to the next, with the host computer keeping track of which
block the CY545 is currently located in.
© 2002 Cybernetic Micro Systems
20
Chapter 5 - Motor Control Commands
ETC [ ETC ]
