DSP

Requests the LM628 calculated desired position from one of the axis controllers.

Mnemonic:

DeSired Position.

Syntax:

DSP $<$n$>$

n: Axis number (0 = azimuth, 1 = elevation)

Return values:

Success:

DSP 1, n, value

Failure:

DSP 0, err_msg

n: The axis number.

value: The desired position for the specified axis. This value can range from $-(2^{30})$ to $(2^{30}) - 1$, although in practice will remain within 2 of revolutions from home ($\pm 200,000$).

err_msg: Should the command fail, this value will be an error message string, explaining the cause of failure. DSP may fail if:

• The wrong number of parameters were supplied.
• The parameter n is non-numeric.
• The parameter n is not `0' or `1'.

Remarks:

The meaning of the desired encoder position depends on whether the move has been completed yet. If it has, then the value returned should be the same as the target position at the time of the last STT command. If the move is ongoing, however, the desired position is the point along the projected trajectory, calculated by the LM628, that the servo should be at when the request is made. Any difference between the desired position and the actual position (see ACP) is the position error. If the position error is significant, this could indicate a servo tuning problem. If the position error is great enough, the LM628 will shut down the motor.

Example:

     send: DSP 1
  receive: DSP 1, 29000

See also:

ABP, ACP, ERL, RDS