Reference Manual

PMAC 2 Software Reference
110 PMAC I-Variable Specifiation
• Bit 1 controls what type of phasing search move is performed, if one is required (Ix74 > 0),
either during power-up/reset, or on a subsequent $ motor reset command. If bit 1 is 0 and a
phasing search move is required, PMAC will use the two-guess phasing search method. If
bit 1 is 1 and a phasing search move is required, PMAC will use the “stepper-motor”
phasing search method. The state of bit 1 does not matter unless a phasing search move is
to be done.
• Bit 2 controls whether an absolute position read for the motor is done at power-up/reset or
not, if one is required (Ix10 > 0). If bit 2 is set to 0 and an absolute position read is
specified, this read operation will be performed automatically at the board power-up/reset.
If bit 2 is set to 1 and an absolute position read is specified, this read operation will not be
done automatically at power-up/reset, and the $* command must be issued to perform the
absolute position read. The state of bit 2 does not matter unless an absolute position read is
to be done.
The possible values of Ix80 and the function of each are described in the following table:
Ix80 Absolute Position Read at
Power-up/Reset?
Phasing Search
Method
Power-up/Reset
Enable State
0 Yes Two-Guess Disabled
1 Yes Two-Guess Enabled
2 Yes Stepper-Motor Disabled
3 Yes Stepper-Motor Enabled
4 No Two-Guess Disabled
5 No Two-Guess Enabled
6 No Stepper-Motor Disabled
7 No Stepper-Motor Enabled
Power-up/reset enable state: If the motor is not automatically enabled at power-up/reset, a
command must be used subsequently to enable the motor. If PMAC is commutating the motor
(Ix01 = 1) and it is a synchronous motor (Ix78 = 0), a phase reference must be established with
the $ or $$ command as part of the enabling process. The motor cannot be enabled before a
successful phase reference is established, because the motor “phase reference error” status bit
that is automatically set on power-up/reset will not have been cleared.
If the motor is either not commutated by PMAC (Ix01 =0) or it is not a synchronous motor
(Ix78 > 0), a simple enabling command can be used. The J/ command enables a single motor;
the A command enables all of the motors in a coordinate system; the <CTRL-A> command
enables all of the motors on PMAC.
The phase reference, whether executed at power-up/reset or on the $ command, can be done
either by reading an absolute position sensor (Ix81 > 0) or by a phasing search move (Ix74 > 0)
if only an incremental sensor is used.
WARNING:
An unreliable phasing search method can lead to a runaway condition.
Test your phasing search method carefully to make sure it works
properly under all conceivable conditions. Make sure your Ix11 fatal
following error limit is active and as tight as possible so the motor will
be killed quickly in the event of a serious phasing search error.
Phasing search move method: The two-guess phasing search is very quick and requires little
movement, but can be adversely affected if there are significant external loads such as friction
and gravity. The stepper-motor phasing search takes more time and causes more movement,
but it is more reliable in the presence of significant external loads.