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M-8888-01P bảng dữ liệu(PDF) 5 Page - Clare, Inc. |
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M-8888-01P bảng dữ liệu(HTML) 5 Page - Clare, Inc. |
5 / 14 page Control Register A Description Bit Name Function Description b0 TOUT Tone output A logic 1 enables the tone output. This function can be implemented in either the burst mode or nonburst mode. b1 CP/DTMF Mode control In DTMF mode (logic 0), the device is capable of generating and receiving DTMF signals. When the call progress (CP) mode is selected (logic 1), a 6th-order bandpass filter is enabled to allow call progress tones to be detected. Call progress tones within the specified bandwidth will be presented at the IRQ/CP pin in rectangular wave format if the IRQ bit has been enabled (b2 = 1). Also, when the CP mode and burst mode have both been selected, the transmitter will issue DTMF signals with a burst and pause of 102 ms (typ) duration. This signal duration is twice that obtained from the DTMF transmit- ter, if DTMF mode had been selected. Note that DTMF signals cannot be decoded when the CP mode has been selected. b2 IRQ Interrupt enable A logic 1 enables the interrupt mode. When this mode is active and the DTMF mode has been selected (b1 = 0), the IRQ/CP pin will pull to a logic 0 condition when either (1) a valid DTMF sig- nal has been received and has been present for the guard time or (2) the transmitter is ready for more data (burst mode only). b3 RSEL Register select A logic 1 selects control register B on the next write cycle to the control register address. Subsequent write cycles to the control register are directed back to control register A. Active Cell Output Frequency(Hz) % Error Specified Actual L1 697 699.1 + 0.30 L2 770 766.2 - 0.49 L3 852 847.4 - 0.54 L4 941 948.0 + 0.74 H1 1209 1215.9 + 0.57 H2 1336 1331.7 - 0.32 H3 1447 1471.9 - 0.35 H4 1633 1645.0 + 0.73 M-8888 www.clare.com 5 Rev. 1 The divider output clocks another counter that addresses the sinewave lookup ROM. The lookup table contains codes used by the switched capacitor D/A converter to obtain discrete and highly accurate DC voltage levels. Two identical circuits are used to produce row and column tones, which are then mixed using a low-noise summing amplifier. The oscillator described needs no startup time as in other DTMF generators, since the crystal oscillator is running con- tinuously, thus providing a high degree of tone burst accuracy. When there is no tone output signal, the TONE pin assumes a DC level of 2.5 volts (typically). A bandwidth limiting filter is incorporated to attenuate distortion products above 4 KHz. Burst Mode: Certain telephony applications require that generated DTMF signals be of a specific duration, determined either by the application or by any of the existing exchange transmitter specifications. Standard DTMF signal timing can be accomplished by making use of the burst mode. The transmitter is capable of issuing symmetric bursts/pauses of predetermined duration. This burst/pause duration is 51 ms ± 1 ms, a standard interval for autodialer and central office applications. After the burst/pause has been issued, the appropriate bit is set in the status register, indicating that the trans- mitter is ready for more data. The timing described in the previous paragraph is available when the DTMF mode has been selected. However, when call progress (CP) mode is selected, a secondary burst/pause time is available that extends this interval to 102 ms ± 2 ms. The extended interval is useful when precise tone bursts of longer than 51 ms duration and 51 ms pause are desired. Note that when CP mode and burst mode have been selected, DTMF tones may be transmitted only and not received. In applications where a nonstandard burst/pause time is desirable, a software timing loop or external timer can be used to provide the timing pulses when the burst mode is disabled by enabling and disabling the trans- mitter. The M-8888 is initialized on powerup sequence with DTMF mode and burst mode selected. Single-Tone Generation: A single-tone mode is available whereby individual tones from the low group or high group can be gener- ated. This mode can be used for DTMF test equipment applications, acknowledgment tone generation, and distortion measurements. Refer to the Control Register B Description below for details. Actual Frequencies vs Standard Requirements |
Số phần tương tự - M-8888-01P |
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Mô tả tương tự - M-8888-01P |
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