Features of SMC3A

 o Using Only a Cheap ATtiny2313 Microcontroller
 o Optimized for Replacement of Stepping Motors
   - Pulse/Dir Command Input with Pulse Multiplyer
   - Pulse rate over 100,000 pulses/sec
   - Gear ratio from 1/256 to 255 in 1/256 step
 o Three Control Modes
   - Relative Positioning Mode
   - Constant Speed Mode
   - Constant Torque Mode
 o Software Decoding of Quadrature Encoder Input
   - Count rate over 100,000 counts/sec in quadrature decoding
   - No External Component is Required
 o Two PWM Outputs for H-bridge Driver
 o Three Diagnostic Outputs
   - Ready, Torque Limit and Servo Error
 o On-the-Fly Servo Tuning


Changes from old SMC

 o Removed G0/G1 Commands
 o Added +/- Commands
   - {+|-}<value>: Increase/Decrease command counter.
 o Extened Pulsed Input Function
   - Pulse Multiplyer: Gear ratio (8.8 fixed-point) can be set with parameter
     #6, 256 means 1.0. Parameter #7 has no effect.
 o Added Diagnostic Outputs
   - Ready: Servo control is running.
   - Torque Limit: Torque limit indicator for mode 2/3.
   - Servo Error: Servo error occured and enterd to mode 0. M command or
     reset can restart servo.
