使用A T90S4414芯片产生双音多频信号

叙述了带有PWM和SRAM的AVR系列微控制器产生双音多频（DTMF）信号的方法，DTMF信呈民可用于电话机以传递拨号信令，DTMF信号是由两个不同频率合成的，表1显示出不同的频率fa和fa合成DTMF音频信号。

DTMF Generator with AT90S4414 chip

This application note describes how DTMF (Dual-Tone Multiple Frequencies) signaling can be implemented using any AVR microcontroller with PWM and SRAM. Applications such as phones are using DTMF signals for transmitting dialing information. There are two frequencies added together to generate a valid DTMF signal,a low fre- quency (fb)and a high frequency (f a ). Table 1 shows how the different frequencies are mixed to form DTMF tones.