Rockwell Automation 4100 AEC Absolute Encoder Converter Installation - Manual (Page 55)

47 Publication 4100-UM052B-EN-P - October 2001
Appendix
B
Strobe Position For Applications Not Using
the 1394 or Compact
Absolute Strobe Cycle When the AEC is connected to controlling hardware other than the
1394 or Compact, the setup must be capable of generating Absolute
Strobe pulses as outlined in this appendix. An Absolute Strobe cycle
is required to obtain the absolute position from the transducer.
The absolute position is transmitted to the controller as a stream of
incremental quadrature pulses on the rising edge of an Absolute
Strobe pulse. The absolute position is transmitted in a two strobe
pulse train sequence. This lets the controller determine the position
of the controlled hardware.
The phase of the encoder output pulses for an absolute strobe is
always positive as defined by A leading B. The absolute position is
transmitted with a sequence of two encoder pulse streams. With the
first absolute strobe (Strobe 1), the lower 16 bits of the transducer
position is transmitted. On the second absolute strobe (Strobe 2), the
9 most significant bits of the transducer position is transmitted (9 bits
of actual data transmitted since only 25 bits are supported). After
completing an absolute update cycle, the position can be calculated
by summing the least significant count with the most significant count
multiplied by 65536 (2
16
). The total maximum number of transducer
counts which can be transmitted is 33554431
(2
25
- 1).
IMPORTANT
Regardless of the number of transducer bits, two absolute
strobe pulses must be sent to the AEC to complete an
absolute position update.
ATTENTION
!
Issuing an Absolute Strobe causes the AEC to stream
position information from the transducer. During this
time, if servo action is enabled by the controlling
hardware, motion can occur. Place your system in a safe
state and disable servo action before performing an
Absolute position update.