看ECT数据手册时，下面这句话有点迷糊。望达人指点。
拜谢！
TSCR2
These three bits specify the number of ¸2 stages that are to be inserted between the bus clock and the main timer counter.
PR2 PR1 PR0 Prescale Factor
0 0 0 1
0 0 1 2
0 1 0 4
0 1 1 8
1 0 0 16
1 0 1 32
1 1 0 64
1 1 1 128
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