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Introduction
Historically, the method of choice for many optical position feedback systems has been A quad B (Quadrature) output. The limitation
of this method is output speed, especially when the interpolation level is high. When the optical sensor speed and/or the
interpolation multiplier is set high, the Quadrature output frequencies will be extremely high and out of the range of the
Quadrature counters of most standard motion controllers.
This limitation can be avoided by sending the position information in parallel format or in a serial word format. The parallel
formats are cumbersome to cable (especially wide word lengths) and are more susceptible to noise interference. Therefore, a
serial data word format is the data communication method of choice.
The Mercury 3000Si Dual Axis Averager Interpolator has the ability to output a position word in a serialized format. This allows
very fast communication between an interpolator and customer application. The speed limitation of the Quadrature format is
thus eliminated.
Signal Description
The interface from your electronics to the Mercury 3000SiDAA interpolator uses four signals, n_spiEnable (n_CS), spiDataOut
(SDO), spiClock (SCK), and optional spiTrigger (TRIG). Each signal is differential and RS-422 compatible. See table for interpolator
signal names, pin names, and pin locations:
Serial Output Specification
Page 11
Signal Description
Signal name Pin Name Function I/O 15 pin HD
Interpolator Connector
Referenced
n_spiEnable n_CS+ Chip Select+ Input 7
n_CS- Chip Select- Input 8
spiClock SCK+ Serial Clock+ Input 14
SCK- Serial Clock- Input 15
spiDataOut SDO+ Serial Data Out+ Output 5
SDO- Serial Data Out- Output 4
spiTrigger TRIG+ External Trigger+ Input 10
TRIG- External Trigger- Input 9
Revision pending.