Single-Chip Voice Recording & Playback Device for Multiple 40- to 60-Second Messages

Page 7

Sampling Application

The following reference schematics are included as exam-

ples on how a recording system might be designed. Each ref-

erence schematic shows the device incorporated in one of its’

three main modes, Random Access, Tape mode - Normal

option, and Tape mode - Auto Rewind option. Note that in

several of the applications either one or all of the /Busy,

/Strobe, or /M7_END pins are connected to LEDs as indica-

tors of device status. This is possible because all of these

pins and signals were designed to have timing compatible

with both microprocessor interface and manual LED indica-

tion. Figure 3 shows the device configured in tape mode, nor-

mal operation. This mode is the minimal part count

application of the APR9600

.

Sampling rate is determined by

the resistor value on pin 7 (OscR). The RC network on pin 19

sets the AGC “attack time”.

A bias must be applied to the electret microphone in order to

power its built in circuitry. The ground return of this bias net-

work is connected to the normally open side of the record

push button. This configuration gates power to microphone

so that it is biased only during recording. This configuration

saves power when not recording by shutting off power to the

electret microphone. Both pins 18 and 19, MicIn and MicRef,

must be AC couple to the microphone network in order to

block the DC biasing voltage.

Figure 3 Tape Mode, Normal Option

/M 1_M essage

/M 2_N ext

/M 3

/M 5

/M 4

/M 6

OscR

/M 7_E N D

/M 8_O ption

/B usy

BE

VSSD

VSSA

SP+

APR9600

V CCD

/R E

ExtC lk

M SEL2

M SEL1

/C E

/S trobe

A na_O ut

A na_In

AG C

MicR ef

MicIn

V CCA

SP-

28

27

26

25

24

23

22

21

20

19

18

17

16

15

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Busy Indicator LED

Vcc

100 k

End Indicator LED

100 k

38 k

Flashing record / play Indicator LED

100 k

220 k

4.7µF

0.1µF

0.1µF

0.1µF

Vcc

22µF

0.1µF

22µF

Vcc

100 k

Rewind switch

Slide action record / playback switch

Play / Record Trigger

Electret

Microphone

1k

4.7k

4.7k

+

_

APR9600

APLUS

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