Performance Motion Devices Juno MC71112, User Manual

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Microstep Waveform Generation
Juno Step Motor Control IC User Guide
51
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By default the Pulse signal is active low however this interpretation, along with that for the Direction and AtRest signals,
is user programmable.
8.6.1.1 Typical Pulse & Direction Processing Circuitry
Figure 8-2:
Pulse &
Direction
Processing
Circuitry
Figure 8-2 shows a typical circuit for processing the Pulse & Direction , and AtRest signals. The buffered signals are
inverted and have a pull-down resistor at the
AtRest
input so the output of the buffer is low to ensure a deterministic
state if AtRest is unconnected.
8.6.2 SPI Signal Interfacing
The table below provides a summary of the SPI related signals:
For complete electrical timing information for SPI bus operations see Section 3.2.3, “Host SPI.”
The only SPI port operation supported by the Juno step motor ICs is a write by the external circuitry of a 16-bit
position command data word. This 16-bit value represents the relative (incremental) distance that the position
command has changed since the previous SPI relative position command write.
The write format is shown in Figure 8-3 . The external circuitry serves as the SPI master generating the clock and the
enable and transmitting the 16-bit data word data to Juno.
AtRest 35 23 AtRest indicates that the axis is at rest and not actively
moving. It is used to select between the 'in motion' pro-
grammable step motor torque levels and the 'at rest'
level.
Pin Name
64-Pin TQFP
Pin#
56-Pin
VQFN Pin# Description and when used
SPIRcv 36 31 SPIRcv inputs synchronous serial data for the SPI bus
SPIXmt 34 30 SPIXmt transmits synchronous serial data for the SPI bus
SPIClock 33 29 SPIClock inputs the clock signal used with synchronous
serial transfer on the SPI bus
SPIEnable 44 39 SPIEnable inputs an enable for SPI bus communications