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(三)双模前置分频器 IC_(17)(MC12013P)是一个高速前置(预)分频器。其典型工作频率为600MHz,具有除10/11等功能。内附V_(BB)参考源,并为时钟提供了缓冲输入。它与IC_(16)(MC12014P)计数控制逻辑电路及IC_(6,5,4,3,2)可编程十进计数器配用,就构成了高速吞脉冲程序分频器,成为频率合成器中的一个重要组成部分,也即是数字可变频标的心脏部分。下面叙述其工作原理。如图5所示,该分频器由除5/6、除2和E-T转换器三个功能单元组成。其中除5/6分频器是由三个D触发器构成,除2电路是将另一个D触发器中的Q和D端相连而构成的,即为T触发器;E-T转换电路如图6所示。因为信号经双模数前置分频器分频后就变成中(低)速信号,所以TTL型的可变程序分频器就可
(C) dual-mode pre-divider IC_ (17) (MC12013P) is a high-speed front (pre) divider. Its typical operating frequency is 600MHz, with the exception of 10/11 and other functions. The V_ (BB) reference is included and provides a buffered input to the clock. It with IC_ (16) (MC12014P) count control logic circuit and IC_ (6,5,4,3,2) programmable decimal counter equipped with high-speed swallow pulse processor to form a frequency synthesizer Is an important part of digital variable frequency that is the heart of the part. The following describes the working principle. As shown in Figure 5, the divider consists of three functional units except 5/6, divide 2, and E-T converters. Which in addition to 5/6 divider is composed of three D flip-flop, with the exception of 2 D flip-flop circuit is connected to the Q and D ends constitute the T flip-flop; ET converter circuit shown in Figure 6 As shown. Because the signal is divided by the dual-modulus prescaler into a (low) speed signal, TTL-type variable program divider can