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DTMF(双音多频)信号的产生与接收是各种DTMF器件应用的基础。利用CPU对DTMF信号产生与接收器件进行管理,可以使DTMF信号产生/接收器件具有智能性,并能灵活地设置多种工作状态,这是DTMF技术应用领域的发展方向。加拿大MITEL公司生产的MT8880芯片是一种能够被CPU管理的DTMF信号产生/接收芯片,由于该芯片被设计为最适合于与MOTOROLA 6800系列单片机总线相配接,故当用Intel 8051系列单片机与之相配接时,电路就比较复杂。本文着重介绍MT8880芯片与MC6802、Intel8051以及国产浪潮0530(CPU为80286,与IBM PC/AT全兼容)微型计算机相配按时的接口电路设计,以及应注意的事项。一、MT8880与MC6802等的接口设计在MT8880与CPU的配接电路中,其内部寄存器操作时钟φ_3的状态非常重要,当MT8880内部寄存器被访问时,φ_2应处于工作状态(至少出现一次带上升沿的高电平);φ_2的工作频率为1kHz～1MHz
The generation and reception of DTMF signals is the basis for various DTMF device applications. The use of CPU to manage the DTMF signal generation and receiving device can make the DTMF signal generating / receiving device intelligent and flexible to set various working states, which is the development direction of DTMF technology application field. MT8880 chip produced by MITEL Company of Canada is a kind of DTMF signal generator / receiver chip which can be managed by CPU. Because the chip is designed to be most suitable for matching with MOTOROLA 6800 series MCU bus, it should be matched with Intel 8051 series single chip microcomputer When connected, the circuit is more complicated. This article focuses on MT8880 chip and MC6802, Intel8051 and domestic Inspur 0530 (CPU is 80286, fully compatible with IBM PC / AT) compatible microcomputer interface circuit design, and should pay attention to the matters. I. Interface Design of MT8880 and MC6802 In the matching circuit of MT8880 and CPU, the state of internal register operation clock φ_3 is very important. When MT8880 internal register is accessed, φ_2 should be in working state (at least one time with rising edge High level); φ_2 operating frequency of 1kHz ~ 1MHz