LM628, LM629

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SNVS781C – JUNE 1999 – REVISED MARCH 2013

Trajectory Control Commands

The following two LM628 user commands are used for setting the trajectory control parameters (position,

velocity, acceleration), mode of operation (position or velocity), and direction (velocity mode only) as required to

describe a desired motion or to select the mode of a manually directed stop, and to control the timing of these

system changes.

LTRJ COMMAND: LOAD TRAJECTORY PARAMETERS

Command Code:

1F Hex

Data Bytes:

Two to Fourteen

Data Ranges…

Trajectory Control

Word:

See Text

Position:

C0000000 to 3FFFFFFF Hex

Velocity:

00000000 to 3FFFFFFF Hex

(Pos Only)

Acceleration:

00000000 to 3FFFFFFF Hex

(Pos Only)

Executable During

Motion:

Conditionally, See Text

Table 5. Derivative-Term Sampling Interval Selection Codes

Bit Position

Selected Derivative

15

14

13

12

11

10

9

8

Sampling Interval

0

0

0

0

0

0

0

0

256

μs

0

0

0

0

0

0

0

1

512

μs

0

0

0

0

0

0

1

0

768

μs

0

0

0

0

0

0

1

1

1024

μs, etc…

thru

1

1

1

1

1

1

1

1

65,536

μs

The trajectory control parameters which are written to the LM628 to control motion are: acceleration, velocity,

and position. In addition, indications as to whether these three parameters are to be considered as absolute or

relative inputs, selection of velocity mode and direction, and manual stopping mode selection and execution are

programmable via this command. After writing the command code, the first two data bytes that are written specify

which parameter(s) is/are being changed. The first byte written is the more significant. Thus the two data bytes

constitute a trajectory control word that informs the LM628 as to the nature and number of any following data

bytes. See Table 6.

Table 6. Trajectory Control Word Bit Allocation

Bit Position

Function

Bit 15

Not Used

Bit 14

Not Used

Bit 13

Not Used

Bit 12

Forward Direction (Velocity Mode Only)

Bit 11

Velocity Mode

Bit 10

Stop Smoothly (Decelerate as Programmed)

Bit 9

Stop Abruptly (Maximum Deceleration)

Bit 8

Turn Off Motor (Output Zero Drive)

Bit 7

Not Used

Bit 6

Not Used

Bit 5

Acceleration Will Be Loaded

Bit 4

Acceleration Data Is Relative

Bit 3

Velocity Will Be Loaded

Bit 2

Velocity Data Is Relative

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