NEC mPD7755 User Manual Download

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Summary of Contents for mPD7755

Page 1: ...USER S MANUAL PD7755 PD7756 NEe...

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Page 3: ...NEC ELECTRONICS EUROPE GMBH 3 85 Vl O USER S MANUAL IlPD7755 IlPD7756...

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Page 5: ...ting popcorn noise in standby mode 3 6 3 3 4 Pin settings in standby mode 3 8 3 4 Start Speech Synthesis 3 8 3 4 1 ST pulse input 3 8 3 4 2 ST fixed input 3 9 3 4 3 Standby mode 3 9 3 4 4 At reset or...

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Page 7: ...ideal for various application systems such as battery driven systems 1 1 Features Synthesizing method Sampling frequency Combined ADPCM and phoneme methods 4 5 6 or 8kHz Bit rate speech 8 to 32kbps Bu...

Page 8: ...10 I 17 I I Messaye se 1 ec t Speech data input memory latch 1 I System Controller f ADPCM decoder Fig 1 1 System Confiyuration 1 2 B Xl X2 I REF W D A tAVO I converter...

Page 9: ...ect input Positive logic is used for these pins high level l Each input is provided with an input latch that latches at the rising edge of the ST input During standby mode these pins should be set to...

Page 10: ...his pin inputs the reference current for the D A converter The output current of the D A current is controlled by the current input to this pin This pin should be connected to VDD via a resistor In st...

Page 11: ...9 VDD This pin should be connected to the power supply 10 GND This pi n should be connected to ground 2 3...

Page 12: ...ut 10 to 20 of the message is made p of silent frames These frames are compressed in the case of the lPD7755 7756 so the actual bit rate is about 80 to 90 of that shown in Table 3 1 Even further reduc...

Page 13: ...d resistance va Potential across RL r _____ 1r r i 0 AVO I 9 bit digital input Fig 3 1 Schematic Diagram of D A Converter 3 2 1 Output Current and Reference Resistance The output current of the D A co...

Page 14: ...sistor can be used as RR EF instead of the variable resistor except for occa sions when the synthesized speed output level must be constant In contrast if the impedance of the amplifier connected to t...

Page 15: ...2 o 200 r 160 120 r 80 L _ t_ _r 40 f_ o 4 _ _4 o 2 3 VREF V 4 Fiy 3 3 Relation Between VRE and IREF I AVO in Low Current Area 3 4...

Page 16: ...st be within the range at which the output transistor of the O A con verter will operate as a constant current supply The operating voltage range is When VOO 5V 1 5V to VOO When Voo 3V lV to VOO The l...

Page 17: ...X2 becomes high level o 10 17 ST CS and RESET inputs are all enabled o The lAVa becomes O 3 3 1 Entering standby mode The IlPD7755 7756 enters the standby mode if the following condition exists for m...

Page 18: ...n response to the standby release signal generated by input of the CS and ST signals see Fig 3 6 The transition time for the O A output is approximately 46 5ms and which enough to suppress this type o...

Page 19: ...as a bus with a floating state they must be pulled up or down 3 4 Start Speech Synthesis Speech synthesi s begins when the signal input to the ST pin goes low when the signal at the CS is already low...

Page 20: ...ation begins when both the ST and CS pins become low level and the BUSY signal is output after the clock oscillation has become stable Then as described in section 3 3 the speech output begins approxi...

Page 21: ...s shifted to 100H and then the speech is output The input to the O A converter is shifted gradually to 100H in the same manner as described in section 3 3 the synthesized speech will be output a maxim...

Page 22: ..._____________________I _____________________ I tSBO I I i i I I 1 i ij S y outlJut tine Speech output start time I I I r I r Speech output 3 Speech output Speech output start t Fig 3 9 Speech Synthesi...

Page 23: ...L I I H BUSY L BUSY output time I I t s o s fl O A converter transition time I Speech output start time O A converter input I 1 I I t DA I tsss I 1 V lFF AVO 1 U0 J speech output OOO rl I Fig 3 10 Spe...

Page 24: ...ed speech output or release the standby mode The PD7755 7756 is reset by holding the RES T pin to low level for the following period of time o During operation 12 oscillator clocks min 18 75 s at 640k...

Page 25: ...resistor shown can be omitted Also in standby mode if the bus to which 10 17 is connected becomes high impedance there is a chance that excess current will drain In this case these signals should alw...

Page 26: ...5 5 I PD7 756 P 10 1 ____ 1 CS Fig 4 1 Circuit Example when Control is by Host Use 5V lO for VOO When a 3V line is used the minimum pulse width for the P07755 7756 ST input becomes 2 s and it no longe...

Page 27: ...ssaye select data in accumulator output contents of accumulator to data bus Check PD775S 7756 BUSY output T f is output with output to bus WR functions as start signal Fig 4 2 Flowchart Control by Hos...

Page 28: ...Voo I essaye select I switch I I I I I I 47kD X8 I PD7755 I PD7756 Voo CS 47kD F ST Start Voo switch 47kD RESET Fig 4 3 Key Input Mode Circuit Example 4 4...

Page 29: ...nd ideally a filter with damping characterics of 48dB oct or better should be used The complexity of such a filter however is prohibitive and we have opted in the interest of simplicity and operabilit...

Page 30: ...O 4 3 Power Amp Because the signal obtained as the output of the lowpass filter described in the preceding paragraph has a wave form identical to that of a normal analog signal this output can be inpu...

Page 31: ...aecause the uPCl212C can operate on voltayes in the ranye of 4 SV t o 7 0V if a 4n speaker is used with S OV power supply a 0 7W THD IOt output is obt ined 4 7...

Page 32: ...re for developing a ROM code for the PD7755 I 7756 is shown in the flowchart in Fig 5 1 The main points of the procedure are described below User NEC User 1 Developmen t de cision Message script Fig 5...

Page 33: ...is reason the use of a professional recording studio using open reel tapes is recommended Also to permit selection of the sample with the best speech quality and the least noise you are asked to provi...

Page 34: ...sampling frequency When 6kHz is specified the frequency bandwidth is almost identical to that of a telephone When 4kHz is selected the bandwidth drops to only those frequencies under 2kHz and there i...

Page 35: ...essage list message selection codes in the same order as messages are recorded on the tape Parameter specification sampling frequency All tapes should include the company name section and name of pers...

Page 36: ...annot assume any responsibility for any circuits shown or represent that they are free from patent Infringement NEe reserves the right to make changes any time without notice by NEG Eleclronlcs Europe...

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Page 40: ...1 314 D 7000 51ullgar130 Tel 0711 890910 Telex 7252220 13 r elux BoschdiJk 187a NL 5612 H8 Eindhoven Tel 040 445845 Telex 51923 sc o ndinavia Box 4039 5 18304 Taby Tel 08 7567245 Telex 13839 Frao r ce...

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