TKR-84038CIRCUIT DESCRIPTION5.3 DSP circuitThe DSP circuit filters transmitter/receiver audio signalsand decodes signaling (QT, DOT). This circuit consists of IC30,IC24, IC27, IC22, IC31, IC34, and IC25. The receiver signalDET is converted from analog to digital by codec IC27 with asampling frequency of 16.128 kHz. The digitized audio signalis sent to DSP IC30 to process the signaling signal and audiosignal. The processed digital audio signal is fed to codec IC27,converted from digital to analog, and the analog signal is outputfrom pin 12 (Vout R). Then, the audio signal is amplified byIC34 (B/2), passes through the IC34 (A/2) low-pass filter, andgoes to multiplexer IC37.The transmitter audio signal coming from pin 13 of IC29 isamplified by IC22 (B/2), fed to pin 6 (Vin R) of codec IC27, andconverted from analog to digital at a sampling frequency of16.128 kHz. The digitized transmitter audio signal is AGCprocessed, pre-emphasized and filtered at 300 Hz to 3 kHz byDSP IC30, and the resulting signal is fed back to codec IC27,converted from digital to analog, and the analog signal is outputfrom pin 15 (Vout L). The transmitter signal from Vout L isamplified by IC34 (B/2), passes through the IC34 (A/2) lowpass filter, and goes to the IC12 (A/2) summing amplifier. IC24is a counter IC and the clock required for the codec and DSPis generated by dividing the 16.515MHz clock signal producedby DSP IC30.C202,-ltC229HI-I I I I 76I AD3 1 a � ! � ; 1 :: £ 5 r ! t � � 2 2 s a � i! ; a a a a 75��---t--+--t1AD3- - ... i D15-..,_,IAD=,c_4 __1-+--IIAD4 A. D14-- GHD! ADSIAD6IAD7IADSIAD9IAD10IADl1c22a I c224C228•• c22e .-,-••-.-+R160l .-cu- CLKGNDl-'-8-Q2!ADSIAD6IAD7IAD6!ADO1.u,10IADllIAD12GHDCLICIN·-ALVDD- CLkOtn'GHDVDD-WR"RDBNS- DNS- PMSIC30I DSPD13D12-GHDD11D10-D9VDDGHD-J;i �DB- fi_3IWRt-++-�IW=R�---",JR!y.,40-IRDt-++-=--=�v,,-....IRD RllO!ALI-++--'"'-"--IALRl!HISo-++--�----"Jlllr-�IS ..GNDl-f+-----'VDDI--++---�IACXt--++---'--"�IADl S1-++==-=--!ACKIAD15IAD141-++==-=-JAD131--++--'-"�-IAD l4IAD13BGBGt-++-=EBGEBGt-++-=BREBR" lilR152IRl82m�IC3l uFig.25 DSP Circuit,__