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四、脉冲吞咽计数的两种预置方式前面提到数据锁存器对主计数器和吞咽计数器的预置有两种方式,在本节中我们将结合具体电路来分别加以介绍。1. 预置所需分频比的方案当我们从键盘输入所需接收的波段和频率数据或从微机的RAM 中调出事先所预置存储的某一频率数据时,微机自动计算出所需分频比N,然后将N 送入数据锁存器中锁存起来。在每一个计数周期开始时数据锁存器将分频比N 预置到由主计数器(N_P)和吞咽计数器(N_S)组成的整个计数链中,达到不同频率下可变分频比的要求。
Four, pulse swallowing the count of two presets Mentioned above data latch on the main counter and swallowing counter preset in two ways, in this section we will be combined with the specific circuit to be introduced separately. 1. Preset the desired frequency division ratio of the program When we input from the keyboard to receive the desired band and frequency data or from the computer’s RAM to recall a predetermined pre-stored frequency data, the computer automatically calculate the required Divide ratio N, then N into the data latch latch. At the beginning of each counting cycle, the data latch presets the frequency division ratio N into the entire counting chain consisting of the main counter (N_P) and the swallowing counter (N_S) to achieve the variable frequency division ratio at different frequencies.