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CY545 Stepper System Controller

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When the CY545 reads the thumbwheel switches, it drives the SW_SEL signal low. Each digit

of the parameter is then read by the two stage read operation. The address of the desired digit

is first generated, and latched by the ALE signal, then the data bus is floated, and the switch

value is enabled during the read strobe signal from RD.

When the entire parameter value has been read, either as 3, 5, or 8 digits, the SW_SEL signal

goes high again, disabling the RD strobe for the switches. A typical thumbwheel switch

parameter read waveforms follows.

Stepper Motor Interface Signals

The CY545 implements eight signals dedicated to the stepper motor, plus the user selectable

function bits, which can generate output control signals for special hardware, or be tested for

special conditions that guide the CY545 through a program of motions, or be used for home

sensor seeking.

PULSE and CWW

The two primary control signals for the motor are PULSE and CCW, which provide the step and

direction indications to the motor. These signals are connected to the external power driver that

actually runs the motor. Every time the CY545 directs the motor to take a step, a signal is

generated on the PULSE line.

The power driver should advance the motor by one increment for each pulse. Note that the step

increment could be a full step, half step, quad step, or micro step. This will be determined by the

application and the power driver. The CY545 does not know or care what the step size is. All

position information is treated in terms of the step increment, not in terms of the linear

displacement or degrees of rotation of the motor.

The CCW signal is a level active signal that tells the power driver in which direction to step the

motor. When high, the driver should step counter clockwise, and when low, the driver should

step clockwise. Note that the physical rotation of the motor will depend on how the motor

windings are connected to the power driver, not on the level of the CCW signal. When this

signal is high, the CY545 will decrement the current position for every step taken, and when the

signal is low, it will increment the current position for every step taken.

© 2002 Cybernetic Micro Systems

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Chapter 16 - Timing and Control