Parker
Hannifin
Encoder Function
This section describes the encoder function of the Axis interface, as well as
signal assignments, electrical/timing characteristics, and internal circuit
schematics.
Modes of Operation
The encoder feature has four modes of operation:
•
Quadrature
•
Step and Direction
•
CW and CCW
•
SSI (Synchronous Serial Interface)
Quadrature Mode
In Quadrature mode, two differential signals drive the onboard circuits:
Encoder CHA and Encoder CHB. When Encoder CHA leads Encoder CHB,
(usually by 90 degrees) the motion is positive by convention. When Encoder
CHA lags Encoder CHB, the motion is negative by convention.
Step and Direction Mode
In Step and Direction mode, two differential signals drive the onboard
circuits: STEP and DIR. A high DIR signal and a positive edge of the STEP
signal indicates a positive count, while a low DIR signal and a positive edge
of the STEP signal indicates a negative count. On the connector, Encoder
CHA and STEP use the same pins and Encoder CHB and DIR use the same
pins.
CW and CCW Mode
In CW and CCW mode, two differential signals drive the onboard circuits:
CW or CCW. A low CCW signal and a positive edge of the CW signal
indicates a positive count. A low CW signal and a positive edge of the CCW
signal indicates a negative count. On the connector, Encoder CHA and CW
use the same pins and Encoder CHB and CCW use the same pins.
SSI Mode
In SSI mode, one differential signal is driven out to a device, and one
differential signal is received from the device: SCLK (clock out) and SDATA
(data in). The first falling edge on SCLK causes the remote device to latch its
current position value. The device then responds by synchronously shifting
the data out using the SCLK rising edge to qualify SDATA. On the connector,
Encoder CHA and SCLK use the same pins, and Encoder CHB and SDATA
use the same pins. For more information on SSI encoders, see Appendix A
on page 109. For more information on SSI mode commands, refer to
ENC
CLOCK,
ENC DST
,
ENC SRC
, and
ENC WIDTH
in the ACR Command
Language Reference (Online Help System in the ACR-View software).
For more information on encoder modes of operation, refer to the
ENC SRC
command in the ACR Command Language Reference (Online Help System
in the ACR-View software).
44 ACR9000 Series Hardware Installation Guide
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