User Manual
Chapter 5
GFK-1742F
Jan 2020
DSM314 to Host Controller Interface
155
CAUTION
An incorrect VLGN value may cause an axis to be unstable. Care should be used when
making any change to the VLGN value.
4.17 Torque Limit. (0.01 percent) Digital Mode and Analog Torque Mode only. The
Torque Limit Command provides a method of limiting the torque produced by the
servomotor. In Analog Torque Mode, the Torque limit value limits the torque
command to a percentage of the full-scale torque command value. Specifically, it
limits the full scale of the analog output where full scale equals 10 volts. The DSM314
will set the Torque Limit at the default 10000 (100 %) whenever a power cycle or
reset occurs. The host controller application logic must set any other value for
desired Torque Limit. The valid range for Torque Limit is 0 to 10000 in units of 0.01%.
This represents 0 - 100 % of peak torque at commanded velocity. If an over- range
value of 10001 - 65535 is sent, the torque limit will be set to 10000. Torque Limit
can be changed during axis motion and takes effect immediately. Refer to the
appropriate servo motor manual for the motor torque curve to determine the actual
value of torque output available at a given velocity. A simple example would be the
use of Torque Limit to prevent over-tightening on a machine.
4.18 Set Aux Encoder Position. (User Units) This command sets the Actual Position value
for an Aux Axis Encoder without using a Find Home operation. The Position Valid %I
bit for the Aux Axis will be set when the command is received.
4.19 Force Servo Velocity. (RPM) Digital Mode and Analog Torque Mode only. This
command bypasses the position loop and forces a velocity command to the digital
servo for tuning purposes. In Analog Torque Mode it bypasses the position loop and
forces a velocity command to the velocity regulator. Acceleration control is not used
and changes in velocity take effect immediately. A Force Servo Velocity command
value of +4095 will produce a motor velocity of + 4,095 RPM and -4095 will produce
a motor velocity of -4,095 RPM (depending on individual motor maximum
velocities). The digital servo control loops may limit actual motor speed to a lower
value. Care should be taken not to operate a servomotor past the rated duty cycle.
The Enable Drive %Q bit must be active with no other motion commanded for the
Force Servo Velocity command to operate. The command must remain
continuously in the %AQ data for proper operation. When a Force Servo Velocity
command is active for a given axis, any other %AQ immediate command for that axis
will remove the Force Servo Velocity data and halt the servo. Chapter 6, Non-
Programmed Motion, also contains information on Force Servo Velocity.
4.20 Select Return Data 1. This command allows alternate data to be reported in the User
Selected Data 1 %AI location for each axis. The alternate data includes information
such as Parameter memory contents and the DSM314 Firmware Revision.
The Select Return Data 1 command uses a mode selection and an offset selection.
The mode selection (byte 1 of the six-byte command) determines the Return
Data type. The offset selection (byte o2, +3 of six-byte command) selects an
individual data item for some modes. Setting the mode to 00h causes the default