AMS DCB-274 manual Find Home, Normally Open Home Switch, Normally Closed Home Switch

ADVANCED MICRO SYSTEMS, INC.				SMC-27X2 SOFTWARE
Command	Function		Type		NV Bytes
F	Find Home		Immediate, Program		3
	Mnemonic	Data 1		Data 2	Result
	(Name) F (n, d)	SPS (40-36,000)		Direction (0,1)	None

F (Find Home)

The special Home algorithm is intended to eliminate mechanical hysteresis typically found in many switches, encoders and is generally present in the form of system mechanical backlash.

The SMC-27X2 microprocessor implements an intelligent homing algorithm whereby home is always approached from the same direction based on the initial logic state of the Home switch and the value (0 or 1) assigned to the “d” direction byte.

Normally Open Home Switch

The Find Home step velocity, using a normally open Home switch (actuation from logic high to low) is programmable over the entire slew velocity available, from 40-36,000 SPS. Once the Home switch is encountered the system inertia typically overshoots the exact switch transition point so that the controller changes the direction signal and shifts the step speed down to the (I) initial parameter velocity. This direction reversal and speed reduction continues until the exact Home switch actuation point is reached and the Homing function is complete.

Normally Closed Home Switch

The Find Home step velocity, using a normally closed Home switch (actuation from logic low to high) will always be the (I) initial velocity parameter setting. Once the Home switch is actuated all motion ceases and the Homing function is complete. The following table illustrates the possible combinations of switch motion:

			“d”
	Home Switch		Parameter		Direction of Motion
	Normally Open (High to Low)		0		Negative
	Normally Closed (Low to High)		0		Positive
	Normally Open (High to Low)		1		Positive
	Normally Closed (Low to High)		1		Negative
	This command may be implemented within a program. Following, is an example:
	P 0	Enter program mode.
	F 1000 1 Find the home switch in the “1” direction at a step rate of 1000 SPS.
	P	Exit program mode.
Command		Function			Type		NV Bytes
G		Execute Program			Immediate, Program		3
		Mnemonic		Data 1		Data 2	Result
		(Name) G (a, t)		0-192, 256-2048		Trace (0-1)	None

G (Go)

The Go command is used to execute a user programmed sequence starting at location “a.” Most programs will start at “0”, however, you may wish to start at another address. The address MUST begin at a stored instruction address, i.e., “go to” data produces unpredictable results.

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