AMS DCB-274 manual Set Jog Speeds, Lower case B Fast and Slow Decay

ADVANCED MICRO SYSTEMS, INC.				SMC-27X2 SOFTWARE
Command	Function		Type		NV Bytes
B	Set Jog Speeds		Default, Immediate, Program		3
	Mnemonic	Data 1		Data 2	Result
	(Name) B (n1, n2)	Slow Speed (0-255)		High Speed (0-255)	None

B (Set Jog Speeds)

These two numbers represent the speeds to use for jog inputs. The first is usually a lower speed. The second number is used when the high-speed jog (pin J1-9) is held low. The values are multiplied by 30 to determine the actual step rate in FULL steps per second. The controller automatically scales the step rates to maintain a constant shaft RPM when the microstep resolution is changed.

Setting values of 0 will disable the jog. Speeds are divided by the “D” value. The power-up settings are stored in NV memory.

This command is generally implemented during the initial customer default parameter assignment. However,

it may be implemented and changed within a program. Following, is an example:
	P 0		Enters program mode.
	B 0 0		Disable jog switches.
	+ 100000		Move 100000 in the plus direction.
	W 0		Wait until move is complete.
	B 30 100		Re-enable jog switches.
	P		Exit program mode.
Command		Function			Type		NV Bytes
b		Set Slow or Fast Decay			Default, Immediate, Program		2
		Mnemonic		Data 1		Data 2	Result
		(Name) b (0, 255)		Speed Threshold			None

b (lower case B; Fast and Slow Decay)

The DCB-274 has been designed to add both Slow and Fast decay. When there is no motion (stopped), the decay will always be slow. The threshold defines a motor speed where slow decay changes to fast decay during acceleration and switches back to slow decay during deceleration. The threshold will occur at an RPM where step resolution is taken into account.

Threshold
Value	½ SPS	1/8 SPS
0	Fast	Fast
25	650	2400
50	1300	4800
100	2400	9600
150	3700	14000
200	5000	19200
255	Slow

Because the step rate is actually measured, the decay detection functions for external step pulse input. Slow decay provides smooth operation with reduced resonance’s at slow to medium speeds. Fast decay will generally enhance high-speed operation at speeds above 200-300 RPM. The actual settings usually must be determined empirically (see Addendum: “About Step Motor Current”) and tailored to the specific design.

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