Motor rotation occurs by sequentially changing the phase and current signals to the two motor coils. Motor speed is controlled by how rapidly the signals are changed. Following is a state table where each state change rotates the document motor rotor 1/400 of a revolution (1/120" of document motion) and there are 8 distinct states before the pattern repeats. Direction of motor rotation can be reversed by moving up rather than down through the state table. The 2 motor windings are labeled Phase A and Phase B and the phase and 2 current level signals for each winding are shown. The state table for the carriage motor is similar but the states with 0% current are skipped so each state change rotates the carriage motor rotor 1/200 of a revolution (1/120" of carriage motion).
Phase A I0A I1A Phase B I0B I1B | A Current | B Current |
| |||||||
1 | 0 | 0 | 1 | 0 | 0 | 100% | Forward | 100% | Forward | |
1 | 0 | 0 | 0 | 1 | 1 | 100% | Forward | 0% | Reverse | |
1 | 0 | 0 | 0 | 0 | 0 | 100% | Forward | 100% | Reverse | |
0 | 1 | 1 | 0 | 0 | 0 | 0% | Reverse | 100% | Reverse | |
0 | 0 | 0 | 0 | 0 | 0 | 100% | Reverse | 100% | Reverse | |
0 | 0 | 0 | 1 | 1 | 1 | 100% | Reverse | 0% | Forward | |
0 | 0 | 0 | 1 | 0 | 0 | 100% | Reverse | 100% | Forward | |
1 | 1 | 1 | 1 | 0 | 0 | 0% | Forward | 100% | Forward | |
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