User manual ARIENS 94400

[. . . ] Data 3, TTL/CMOS level, input to set data bit 3 in data word. Data 2, TTL/CMOS level, input to set data bit 2 in data word. Data 1, TTL/CMOS level, input to set data bit 1 in data word. Data 0, TTL/CMOS level, input to set data bit 0 in data word. [. . . ] A 7-bit DAC which is monotonic to 7 bits simply means that increasing digital input codes will produce an increasing analog output. s FUNCTIONAL DESCRIPTION Each DAC channel contains one register and a D/A converter. A block diagram is shown on the first page. The sign outputs generate the phase shifts, i. e. , they reverse the current direction in the phase windings. Data Bus Interface 94400 is designed to be compatible with 8-bit microprocessors such as the 6800, 6801, 6803, 6808, 6809, 8051, 8085, Z80 and other popular types and their 16/32 bit counter parts in 8 bit data mode. The data bus interface consists of 8 data bits, write signal, chip select, and two address pins. All inputs are TTL-compatible (except reset). The address pin control data transfer to the two internal D-type registers. Data is transferred according to figure 7 and on the positive edge of the write signal. Output Output Output Actual Gain error Correct Endpoint non-linearity More than 2 bits Less than 2 bits Negative difference Positive difference Offset error Input Input Full scale Input Figure 3. Differential non-linearity of more than Differential non-linearity of less than 1 bit, output is non-monotonic. 1 bit, output is monotonic. Figure 5. The number of true microsteps that can be obtained depends upon many different variables, such as the number of data bits in the Digital-to-Analog converter, errors in the converter, acceptable torque ripple, single- or double-pulse programming, the motor's electrical, mechanical and magnetic characteristics, etc. Many limits can be found in the motor's ability to perform properly; overcome friction, repeatability, torque linearity, etc. It is important to realize that the number of current levels, 128 (27), is not the number of steps available. 128 is the number of current levels (reference voltage levels) available from each driver stage. Combining a current level in one winding with any of 128 other current levels in the other winding will make up 128 current levels. So expanding this, it is possible to get 16, 384 (128 · 128) combinations of different current levels in the two windings. Remember that these 16, 384 micropositions are not all useful, the torque will vary from 100% to 0% and some of the options will make up the same position. For instance, if the current level in one winding is OFF (0%) you can still vary the current in the other winding in 128 levels. All of these combinations will give you the same position but a varying torque. Typical Application The microstepper solution can be used in a system with or without a microprocessor. Without a microprocessor, a counter addresses a ROM where appropriate step data is stored. [. . . ] For good motor performance, controlled acceleration and deceleration should be considered even though microstepping will improve overall performance. 94400 Time when motor is in a compromise position. Time Useful time = correct position Double pulse write signal Ideal data = desired position Actual data = true position Normal resolution Write time = incorrect position Figure 10. Double pulse programming, in- and output signals. Time when motor is in an intermediate position. Time when micro position is almost correct. [. . . ]