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Upload Absolute Position from a C3 to a ACR9000

If you were using a Compax3 I10T10, an ACR9000 and a motor with an absolute encoder, it would be beneficial to get the absolute position from the encoder to the ACR9000. This would eliminate the need to home the system, which is most of the reason for an absolute encoder. This can be done since the ACR9000 has an RS485 output on every Axis connector that can be used for any communications and the Compax3 has a RS485 port. Follow the sections below for the details on the Cabling, Compax3 Setup and the ACR9000 Setup.


71-021108-XX ACR to Compax3 cable, where XX is your length in feet
71-021609-01 ACR axis/communications breakout (Aries Dongle)

The above cables will provide you with one ACR9000 connection, a RS485 9 pin connector and 2 connections at the Compax3 drive. Both units' should have the same ground reference with the back of the Compax3 and ACR9000 installed to the same bare metal cabinet (not painted) or if in separate cabinets, their grounds should be tied together with a large braided shielded wire, as short as possible. At this point all the connections are made to make motion from the ACR9000 to the Compax3. The only thing left is a communications cable between the two.

ACR9000 to Compax3 Communication Cable
71-021609-01 9-Pin D-Sub Pin # Compax3 X10 Pin # Function
2 7 RS485 +
3 3 RS485 -
5 5 Ground

Connect Pins 1 and 9 on the Compax3 X10 connector to enable RS485 on the Compax3.
Compax3 Setup

After configuring the motor you will need to setup the RS485 objects.

810.1 is the RS485 Protocol (Use 16 for 2 wire setup)
810.2 is the RS485 Baud Rate
810.3 is the RS485 Node Address

These can be set from the Optimization screen in the Servomanager software or from an ASCII terminal. See the FAQ "Accessing Objects from RS232 and RS485" for more details on setting objects.

Set 810.1 = 16, 810.2 = 9600, 19200 or 38400 and finally set the node address to some number between 1 and 97. Make sure to write these values to the flash by pressing the "WF" button in the Optimization screen or writing a non-zero number to the 20.11 object.

ACR9000 Setup

With all the Cabling and Compax3 Setup complete, you should now be able to open the comm port on the ACR9000 and talk to the Compax3. This is done in 4 simple steps.

1) Type 'OPEN "COM2:nnnn,N,8,1" AS #1' where nnnn is the baud rate set on the RS485 Baud rate object of the Compax3.
If using the ACR9000's 9pin com port it would be COM1; this 9pin is RS485 4wire.

2) Using Hyperterminal, type 'TALKTO #1' This will start an interface directly to the Compax3 from the ACR9000 terminal. Do not use ACR-View for this step. TALKTO in ACR-View will not connect; user Windows Hyperterminal.

3) Type 'no680.5' where n is the RS485 address number on the Compax3, and hit enter. This should return the value of the actual position of the motor. If there is no response, make sure the Compax3 is powered as well as the Cabling and RS485 settings are correct.

4) Hit the escape key to exit this mode.
Finally to automate the process the below code should be implemented on power up to get the actual position and reset the position counters in the ACR9000 to the absolute number.

DIM $V(10,80)
OPEN "COM2:9600,N,8,1" AS #1
DWL 0.5
$V0 = "1o680.5" + CHR$(13)
PRINT #1, $V0;
INPUT; #1, $V1
$V1 = MID$($V1,2,LEN($V1)-2)
DV0 = VAL($V1)

Please note that the actual position from the Compax3 drive will return in revolutions of the motor. You may need to scale this number to get the desired units for the application.