Reading The Absolute Position With Communication - Delta ASDA-A3 Series User Manual

Absolute System

10.3.7 Reading the absolute position with communication

You can access the data of the absolute encoder through two communication methods: instant
access or parameter access. Instant access refers to reading the motor's feedback position as
10
soon as power is sent to the servo. When you set the status monitoring register 1 to the motor's
feedback pulse number (P0.017 = 0), you can access the motor's current position by reading
P0.009. Parameter access means the motor's position is temporarily stored in parameters. Once
you set P0.049 with communication, the encoder's status, absolute position (cycle number), and
pulse number (or PUU) are stored in P0.050, P0.051, and P0.052 respectively. You can choose
to read the pulse number or PUU through P2.070 Bit 1. Even when the motor is stopped, it still
moves slightly forward and backward. When you set P0.049 to 1, the encoder continues to read
the exact position where the motor stops without changing anything else. On the other hand,
when you set P0.049 to 2, the encoder updates the motor's current position on the servo drive,
which clears the position error.
For example, the motor's current position is 20000, but it varies between 19999 and 20001.
If you send the command to read the motor's position when it stops at 20001, the motor's
position is updated to 20001. After all positions are updated in P0.050 – P0.052, P0.049 is
automatically reset to 0. At that point, the controller can access the values of P0.050 – P0.052.
P0.050 shows the status of the absolute encoder. When it shows absolute position lost or
overflow, that indicates that the absolute position is invalid. You must re-do the homing
procedure and re-initialize the absolute coordinates.
10-20
Start
Set P0.049 to 1 or 2
No
P0.049 = 0
Yes
Read
P0.050 - P0.052
Stop
ASDA-A3
Revision December, 2017