CHAPTER 3
3.4.2 Motor Control Circuitry
Figure 3-4 shows the Motor Control Circuitry. Stepper Motor inputs PHASE 1 through PHASE 4 determine the direction of rotation and stepping verses fractional stepping. The micro controller loads data into registers U26 and U27 through activation of CS MOT. This data determines the operation of U28. U28 then generates the associated phase signals. For each of its operations, U28 also requires specific reference voltages. Two resistor ladder networks in association with outputs from U26 and U27 form digital-to-analog converters. Therefore, for each loading of U26 and U27, the micro controller also includes data that determines the reference voltages sent to U28.
The Micro Controller, through signals sent to U29, determines which dc motor is enabled. U21 has quad
The Micro Controller enables U28 via the CDE ALIM signal, which activates K1. Programmable potentiomenters inside U20 determine the U28 output voltage. The Micro Controller establishes U20 resistances via the U20 Serial Input (SD1) and an associated clock (SCLK). The Micro Controller activates CS POT to
