CY545 Stepper System Controller
www.ControlChips.com
Also note that the CCW signal can be used as an input, to force stepping in the desired
direction. In this case, the software direction command should be set to “-”, so the CY545 tries
to drive the CCW signal high. Now an external circuit can easily override the CY545, and force
the CCW signal low, causing stepping in the "+" direction. If this is tried while the CY545 is
driving the CCW signal low, a much stronger external circuit will be required to override the
CY545, since it has much stronger sink current capability than source current capability. This
could ultimately burn out the CCW signal, and should be avoided if possible.
Several PULSE signal waveforms are shown below, for different step rates. Notice that the
PULSE signal is normally high, and goes low at the beginning of a step. It stays low for a fixed
amount of time, which depends on the crystal frequency of the CY545, and then goes back high
for the duration of the step time. When it is time for the next step, PULSE goes low again.
When the step rate parameters are set to enable acceleration, the CY545 will vary the step rate
from the starting rate (First Rate parameter) to the final rate (Rate parameter) for each motion it
takes. This means the PULSE waveform will vary from the slower rate to the faster rate as the
CY545 accelerates the motor up to the slew rate, and then will be stable for the duration of the
slewing period. The CY545 will determine when to begin deceleration so that the motor will slow
down again to the starting rate as the desired number of steps has expired.
© 2002 Cybernetic Micro Systems
68
Chapter 16 - Timing and Control
ETC [ ETC ]
