PMAC Product Guide This makes the jog command for a jog-until trigger something like J=10000^100 , J=*^-50 or J:50000^0 . The value before the ^ is the destination position or distance (depending on the type of jog command) to be traveled in the absence of a trigger. If this first value is represented by a * symbol, PMAC looks in a pre-defined register for the position or distance. The second value is the distance to be traveled relative to the position at the time of the trigger. This value is always expressed as a distance, regardless of the type of jog command. Both values are expressed in encoder counts. The trigger condition for the motor is set up just as for homing search moves:
• Ix03 bit 17 specifies whether input flags are used to create the trigger, or the warning following error limit status bit is the trigger (torque-limited triggering): 0=flags, 1=error status. • If input flags are to create the trigger, Ix25 specifies the flag register. • If input flags are to create the trigger, Encoder/Flag I-Variables 2 and 3 for this set of flags specify which edges of which signals will cause the trigger.
• Ix03 bit 16 specifies whether the hardware-captured counter value is used as the trigger position -- suitable for incremental encoder signals, real or simulated -- or the software-read position is used instead -- suitable for other types of feedback (0=hardware, 1=software). The software-read position must be used if the following error status is used for the trigger. PMAC will use the jog parameters Ix19-Ix22 in force at the time of the command for the pre-trigger move and the values of these parameters in force at the time of the trigger for the post-trigger move. The captured value of the sensor position at the trigger is stored in a dedicated register if later access is needed.
The units are in counts; for incremental encoders, they are relative to the power-up/reset position. PMAC sets the motor home-search-in-progress status bit (bit 10 of the first motor status word returned on a ? command) true (1) at the beginning of a jog-until-trigger move. The bit is set false (0) either when the trigger is found, or at the end of the move. In addition, PMAC sets the motor trigger move status bit (bit 7 of the second motor status word returned on a ? command) true at the beginning of a jog-until-trigger move, and keeps it true at least until the end of the move.
If a trigger is found during the move, this bit is set false at the end of the post-trigger move; however, if the pre-trigger move finishes without finding a trigger, the bit is left true at the end of the move. Therefore, this bit can be used at the end of the move to tell whether the trigger was found successfully or not. The motor desired-velocity-zero status bit can be used to determine the end of the move. Homing Search Moves Homing Acceleration The acceleration for homing search moves is controlled by the same parameters -- Ix19, Ix20, and Ix21 -- as for jogging moves. These are described in the above section. Homing Speed Homing speed and direction are specified by Ix23.
If Ix23 is greater than zero, the homing search move will be positive. If it is less than zero the move will be negative. The magnitude of Ix23 controls the speed of the move (in counts/msec). Programming PMAC 57