MT8888中文说明

1功能描述The MT8888C Integrated DTMF Transceiver consists of a high performance DTMF receiver with an internal gain该MT8888C集成DTMF收发器包括一个内部获得高性能的DTMF接收器setting amplifier and a DTMF generator which employs a burst counter to synthesize precise tone bursts and设置放大器和一个DTMF发生器采用合成反爆裂爆裂及精确的音调pauses. A call progress mode can be selected so that frequencies within the specified passband can be detected.停顿。呼叫过程模式可供选择，所以，在指定的通带频率可以被检测到。The Intel micro interface allows microcontrollers, such as the 8080, 80C31/51 and 8085, to access the MT8888C英特尔微型接口允许微控制器，如8080，51和8085的80C31，访问了MT8888Cinternal registers.内部寄存器。2.0 Input Configuration2输入配置The input arrangement of the MT8888C provides a differential-input operational amplifier as well as a bias sourceMT8888C的输入装置提供了一个差分输入运算放大器以及一个偏置源(VRef), which is used to bias the inputs at VDD/2. Provision is made for connection of a feedback resistor to the opamp（VREF），这是用于偏置输入到VDD / 2。设置了一个反馈电阻连接到运算放大器output (GS) for gain adjustment. In a single-ended configuration, the input pins are connected as shown in输出（GS）增益调整。在一个单端配置，输入引脚连接，如图所示Figure 3. Figure 4 shows the necessary connections for a differential input configuration.图3。图4显示了一个差分输入配置必要的连接。3.0 Receiver Section3接收机部分Separation of the low and high group tones is achieved by applying the DTMF signal to the inputs of two sixth-order的高、低组色调分离是通过应用DTMF信号的六分之二阶输入实现switched capacitor bandpass filters, the bandwidths of which correspond to the low and high group frequencies开关电容滤波器的带宽，其中对应于低，高剂量组的频率(see Table 1). These filters incorporate notches at 350 Hz and 440 Hz for exceptional dial tone rejection. Each filter（见表1）。这些过滤器采用缺口在350 Hz和440 Hz的特殊拨号音拒绝。每个过滤器output is followed by a single order switched capacitor filter section, which smooths the signals prior to limiting.输出是由一个单一的阶开关电容滤波器部分，它平滑的信号之前限制。Limiting is performed by high-gain comparators which are provided with hysteresis to prevent detection of限制是通过高增益比较器具有滞后防止检测的执行unwanted low-level signals. The outputs of the comparators provide full rail logic swings at the frequencies of the不必要的低电平信号。该比较器输出提供完整的逻辑摆幅轨的频率incoming DTMF signals.输入的DTMF信号。Following the filter section is a decoder employing digital counting techniques to determine the frequencies of the经过筛选的第一个解码器是采用数字计数技术来确定的频率incoming tones and to verify that they correspond to standard DTMF frequencies. A complex averaging algorithm传入的音调，以验证它们是差和变化。这种平均算法已被开发，以确保最佳的组合immunity to talk-off and tolerance to the presence of interfering frequencies (third tones) and noise. When the谈小康和容忍的干扰频率存在免疫（第三吨）和噪声。什么时候detector recognizes the presence of two valid tones (this is referred to as the “signal condition” in some industry探测器承认存在两个有效的色否符合标准的DTMF信号频率。平均一个复杂的算法protects against tone simulation by extraneous signals such as voice while providing tolerance to small frequency防止如语音信号的干扰音仿真在小频率提供公差deviations and variations. This averaging algorithm has been developed to ensure an optimum combination of偏调（这被称为“信号”在某些行业specifications) the “Early Steering” (ESt) output will go to an active state. Any subsequent loss of signal condition规格）的“早转向”（EST）的产量将进入一个积极的状态。随后的任何信号损失条件will cause ESt to assume an inactive state.将导致美国东部时间承担无效状态。4 控制电路Before registration of a decoded tone pair, the receiver checks for a valid signal duration (referred to as character前一个解码语气对注册，一个有效的时间信号接收机检查（简称字符recognition condition). This check is performed by an external RC time constant driven by ESt. A logic high on ESt识别条件）。由一个外部RC时间常数的预测驱动的这是执行检查。逻辑高ESTcauses vc (see Figure 5) to rise as the capacitor discharges. Provided that the signal condition is maintained (ESt风险投资的原因（见图5）上升为电容放电。提供的信号条件下保持（ESTremains high) for the validation period (tGTP), vc reaches the threshold (VTSt) of the steering logic to register the仍然很高）的有效期（tGTP），VC达到阈值（VTST）的转向逻辑寄存器tone pair, latching its corresponding 4-bit code (see Table 1) into the Receive Data Register. At this point the GT双音，保持其相应的4位代码（见表1）在接收数据寄存器。在这一点上，GToutput is activated and drives vc to VDD. GT continues to drive high as long as ESt remains high. Finally, after a输出被激活和带动VC VDD。燃气轮机继续推动高只要EST仍然很高。最后，经过short delay to allow the output latch to settle, the delayed steering output flag goes high, signalling that a received短暂的延迟，使输出锁存器来解决，延迟转向输出标志走高，这表明收到tone pair has been registered. The status of the delayed steering flag can be monitored by checking the appropriate的语气对已经登记。的延迟转向标志的状态可以通过检查适当的监测bit in the status register. If Interrupt mode has been selected, the IRQ/CP pin will pull low when the delayed steering位在状态寄存器。如果中断模式已被选中，IRQ / CP销将拉低时延迟转向flag is active.标志是积极的。The contents of the output latch are updated on an active delayed steering transition. This data is presented to the的输出锁存器的内容是一个活跃的延迟转向过渡更新。这个数据是到了four bit bidirectional data bus when the Receive Data Register is read. The steering circuit works in reverse to四位双向数据总线在接收数据寄存器读取。控制电路工作在反向validate the interdigit pause between signals. Thus, as well as rejecting signals too short to be considered valid, the receiver will tolerate signal interruptions (drop out) too short to be considered a valid pause. This facility, together验证之间的信号interdigit(指间)暂停。因此，以及拒绝信号太短，被认为是有效的，接收器将信号中断的容忍（降）太短，被认为是一种有效的暂停。这一设施，在一起with the capability of selecting the steering time constants externally, allows the designer to tailor performance to随着选择转向时间常数的外部能力，允许设计师量身定制的性能meet a wide variety of system requirements.满足各种各样的系统要求。5 保护时间调整The simple steering circuit shown in Figure 5 is adequate for most applications. Component values are chosen简单的控制电路如图5所示是最适当的应用。元件值的选择according to the following inequalities (see Figure 7):根据下列不等式（见图7）：The value of tDP is a device parameter (see AC Electrical Characteristics) and tREC is the minimum signal duration该计划书的价值是一个设备参数（见交流电气特性）和TREC是最低的信号持续时间to be recognized by the receiver. A value for C1 of 0.1 F is recommended for most applications, leaving R1 to be是由接收器认可。0.1C1的F值是最推荐的申请，离开R1是selected by the designer. Different steering arrangements may be used to select independent tone present (tGTP)由设计者选择。不同的指导安排，可以用来选择独立音目前（tGTP）and tone absent (tGTA) guard times. This may be necessary to meet system specifications which place both accept音无（tGTA）保护时间。这可能是要符合系统规范的地方都接受and reject limits on tone duration and interdigital pause. Guard time adjustment also allows the designer to tailor拒绝限制音的持续时间和间歇。保护时间的调整也允许设计者的裁缝system parameters such as talk off and noise immunity.系统参数，如谈话和噪声免疫力。Increasing tREC improves talk-off performance since it reduces the probability that tones simulated by speech will增加tREC提高通话起飞性能，因为它减少了音调将模拟语音的概率maintain a valid signal condition long enough to be registered. Alternatively, a relatively short tREC with a long tDO保持一个有效的信号状态足够长的时间进行登记。另外，一个有着悠久的TDO较短的TRECwould be appropriate for extremely noisy environments where fast acquisition time and immunity to tone drop-outs将非常适合在嘈杂的环境下，快速采集时间和音落免疫计划are required. Design information for guard time adjustment is shown in Figure 6. The receiver timing is shown in是必需的。保护时间调整的设计信息，如图6所示。接收时间显示Figure 7 with a description of the events in Figure 9.图7描述了图9中的事件。6.0 Call Progress Filter一个呼叫过程模式，使用了MT8888C，可以选择允许各种色调的检测，识别the progress of a telephone call on the network. The call progress tone input and DTMF input are common,网络上的电话呼叫进展。呼叫进展音输入DTMF输入是常见的，however, call progress tones can only be detected when CP mode has been selected. DTMF signals cannot be然而，呼叫进程音只能检测到CP模式已被选中。DTMF信号不能detected if CP mode has been selected (see Table 7). Figure 8 indicates the useful detect bandwidth of the call如果CP模式已被选定的检测（见表7）。图8显示了有用的检测呼叫的带宽progress filter. Frequencies presented to the input, which are within the accept bandwidth limits of the filter, are进步滤波器。提出了对输入的频率，这是在“接受”的滤波器带宽的限制，是hard-limited by a high gain comparator with the IRQ/CP pin serving as the output. The squarewave output obtained硬限制由高增益比较器的IRQ / CP引脚作为输出。方波输出from the schmitt trigger can be analyzed by a microprocessor or counter arrangement to determine the nature of由施密特触发器可以由一个微处理器或柜台安排确定的性质分析the call progress tone being detected. Frequencies which are in the reject area will not be detected and呼叫进展音检测。的频率是在“拒绝”地区将不会被检测到consequently the IRQ/CP pin will remain low.,因此IRQ / CP引脚将保持低。7 .0 DTMF发生器The DTMF transmitter employed in the MT8888C is capable of generating all sixteen standard DTMF tone pairs采用DTMF发送器MT8888C中能产生的所有十六个标准的DTMF双with low distortion and high accuracy. All frequencies are derived from an external 3.579545 MHz crystal. The低失真、高精度。所有的频率都是来自外部3.579545 MHz的晶体。的sinusoidal waveforms for the individual tones are digitally synthesized using row and column programmable对于个别音调正弦波形使用的行和列的可编程数字合成dividers and switched capacitor D/A converters. The row and column tones are mixed and filtered providing a分频器和开关电容的D / A转换器。行和列的音调混合和过滤提供DTMF signal with low total harmonic distortion and high accuracy. To specify a DTMF signal, data conforming to the与低总谐波失真和高精度的DTMF信号。指定一个DTMF信号，符合数据encoding format shown in Table 1 must be written to the transmit Data Register. Note that this is the same as the编码格式如表1所示，必须写入发送数据寄存器。请注意，这是一样的receiver output code. The individual tones which are generated (fLOW and fHIGH) are referred to as Low Group and接收器的输出代码。所产生的个别音调（流量和高）被称为低组和High Group tones. As seen from the table, the low group frequencies are 697, 770, 852 and 94 Hz. The high group高剂量组色调。正如从表中看出，低组的频率是697，770，852和94赫兹。高剂量组frequencies are 1209, 1336, 1477 and 1633 Hz. Typically, the high group to low group amplitude ratio (twist) is 2 dB频率是1209，1336，1477和1633赫兹。通常情况下，低组振幅比大集团（扭曲）是2分贝to compensate for high group attenuation on long loops.为了弥补群体高衰减对长的循环。The period of each tone consists of 32 equal time segments. The period of a tone is controlled by varying the length每个音调周期由32个相等的时间段。一个音调周期的不同长度的控制of these time segments. During write operations to the Transmit Data Register the 4 bit data on the bus is latched这些时间段。在写操作到发送数据寄存器的4位数据总线上的锁and converted to 2 of 8 coding for use by the programmable divider circuitry. This code is used to specify a time转换为2 8编码使用的可编程分频器电路。本代码是用于指定一个时间segment length, which will ultimately determine the frequency of the tone. When the divider reaches the appropriate段的长度，这将最终确定的音调的频率。当分压达到适当的count, as determined by the input code, a reset pulse is issued and the counter starts again. The number of time计数，由输入码确定，复位脉冲发出和计数器重新开始。时间的数segments is fixed at 32, however, by varying the segment length as described above the frequency can also be段是固定在32，但是，通过不同的段长度为上述频率也可以varied. The divider output clocks another counter, which addresses the sinewave lookup ROM.不同的。分压器的输出时钟，另一个柜台，其中涉及的正弦波查找ROM。查找表包含的代码是由开关电容的D / A转换器获得离散和使用highly accurate DC voltage levels. Two identical circuits are employed to produce row and column tones, which高度精确的直流电压水平。两个相同的电路是用来产生的行和列的音调，这are then mixed using a low noise summing amplifier. The oscillator described needs no “start-up” time as in other然后混合使用低噪声加法放大器。振荡器的描述不需要启动时间在其他DTMF generators since the crystal oscillator is running continuously thus providing a high degree of tone burstDTMF发生器由于晶体振荡器是连续运行提供高程度的纯音accuracy. A bandwidth limiting filter is incorporated and serves to attenuate distortion products above 8 kHz. It can精度。一个带宽限制滤波器相结合，用于衰减失真的产品超过8千赫。它可以be seen from Figure 8 that the distortion products are very low in amplitude.从图8，失真的振幅是非常低的看到产品。8突发模式In certain telephony applications it is required that DTMF signals being generated are of a specific duration在某些电话的应用，它是必需的，DTMF信号的产生是一个特定的时间determined either by the particular application or by any one of the exchange transmitter specifications currently确定由特定的应用程序或由交易所发送任何一个规格目前existing. Standard DTMF signal timing can be accomplished by making use of the Burst Mode. The transmitter is现有的。标准的DTMF信号的时间可以利用突发模式的实现。发射机capable of issuing symmetric bursts/pauses of predetermined duration. This burst/pause duration is 51 ms1 ms,能够发出阵阵/停留预定持续时间的对称。这一阵/暂停持续时间为51毫秒1毫秒，which is a standard interval for autodialer and central office applications. After the burst/pause has been issued, the这是自动拨号器和中央办公应用的标准区间。爆裂后/暂停已经发出，该appropriate bit is set in the Status Register indicating that the transmitter is ready for more data. The timing适当的位被设置在显示发射准备更多的数据状态寄存器。定时described above is available when DTMF mode has been selected. However, when CP mode (Call Progress mode)上述时可用DTMF模式已被选中。然而，当CP模式（呼叫过程模式）is selected, the burst/pause duration is doubled to 102 ms 2 ms. Note that when CP mode and Burst mode have被选中，爆裂/暂停时间增加一倍到102毫秒2毫秒。注意在CP模式和突发模式been selected, DTMF tones may be transmitted only and not received. In applications where a non-standard被选定，DTMF音调可以只发送不接受。在应用非标准burst/pause time is desirable, a software timing loop or external timer can be used to provide the timing pulses爆裂/暂停时间是可取的，一个软件定时循环或外部定时器可用于提供定时脉冲when the burst mode is disabled by enabling and disabling the transmitter.当突发模式是通过启用和禁用发射机残疾人。9 代单色调A single tone mode is available whereby individual tones from the low group or high group can be generated. This一个单一的音调模式是可用的，从低组和高组可以产生个别音调。这mode can be used for DTMF test equipment applications, acknowledgment tone generation and distortion模式可用于DTMF测试设备的应用，确认音的产生和失真measurements. Refer to Control Register B description for details.测量。是指控制寄存器B中描述的细节。10.0 Distortion Calculations10的失真计算The MT8888C is capable of producing precise tone bursts with minimal error in frequency (see Table 2). The该MT8888C能够与频率的纯音的最小误差产生精确的（见表2）。的internal summing amplifier is followed by a first-order lowpass switched capacitor filter to minimize harmonic内部加法放大器是由一阶低通开关电容滤波器减少谐波components and intermodulation products. The total harmonic distortion for a single tone can be calculated using组件和互调产物。一个单一的色调总谐波失真可以计算Equation 1, which is the ratio of the total power of all the extraneous frequencies to the power of the fundamental方程1，这是所有多余的频率总功率的基本功率比frequency expressed as a percentage.频率表示为一个百分比。The Fourier components of the tone output correspond to V2f. Vnf as measured on the output waveform. The total的音调输出的傅里叶分量对应于V2F的VNF为输出波形测量。总harmonic distortion for a dual tone can be calculated using Equation 2. VL and VH correspond to the low group对于一个双音谐波失真可以计算方程2。对应于低组，VL、VHamplitude and high group amplitude, respectively and V2振幅、高振幅组，分别和V2IMD is the sum of all the intermodulation components. TheIMD是所有的互调分量之和。的internal switched-capacitor filter following the D/A converter keeps distortion products down to a very low level as内部开关电容滤波器的D / A转换器保持失真产品降到很低的水平以下shown in Figure 10.图10所示。11.0 DTMF Clock Circuit11个DTMF时钟电路The internal clock circuit is completed with the addition of a standard television color burst crystal. The crystal内部时钟电路完成的标准电视彩色爆裂晶体加。晶体specification is as follows:规格如下：Frequency: 3.579545 MHz频率：3.579545兆赫Frequency Tolerance: 0.1%频率公差：0.1%Resonance Mode: Parallel共振模式：平行Load Capacitance: 18pF负载电容：18pFMaximum Series Resistance: 150 ohms最大串联电阻：150欧姆Maximum Drive Level: 2mW最大的驱动电平：2MWe.g. CTS Knights MP036S例如mp036s CTS骑士Toyocom TQC-203-A-9S东洋tqc-203-a-9sA number of MT8888C devices can be connected as shown in Figure 13 such that only one crystal is required.一些MT8888C设备可连接如图13中，只有一个水晶是必需的证明。Alternatively, the OSC1 inputs on all devices can be driven from a TTL buffer with the OSC2 outputs left另外，在所有设备OSC1输入可驱动与OSC2 TTL输出缓冲区的左unconnected.无关。12 单片机的接口The MT8888C incorporates an Intel microprocessor interface which is compatible with fast versions (16 MHz) of the这包含了一个英特尔微处理器接口MT8888C的快速版本兼容（16 MHz）的80C51. No wait cycles need to be inserted.80C51。没有等待周期需要插入。Figure 19 and Figure 20 are the timing diagrams for the Intel 8031, 8051 and 8085 (5 MHz) microcontrollers. By图19和图20是英特尔8031的时序图，8051，8085（5 MHz）的微控制器。通过NANDing the address latch enable (ALE) output with the high-byte address (P2) decode output, CS is generated.南定地址锁存使能（ALE）与高字节地址输出（P2）解码输出，CS产生。Figure 14 summarizes the connection of these Intel processors to the MT8888C transceiver.图14总结了这些英特尔处