Datasheet

LM628, LM629
www.ti.com 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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