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ISDMICROTAD-16ME

Single-Chip Voice Record/Playback Device 16-Minute Duration

Information Storage Devices 

ISD MicroTAD-16M

NON-INVERTING ANALOG INPUT (ANA IN+)

This pin is the non-inverting analog input that

transfers the signal to the device for recording.

The analog input amplifier can be driven single

ended or differentially. In the single-ended input

mode, a 32 mVp-p (peak-to-peak) maximum sig-

nal should be capacitively connected to this pin

for optimal signal quality. This capacitor value,

together with the 3 KΩ input impedance of ANA

IN+, is selected to give cutoff at the low frequen-

cy end of the voice passband. In the differential-

input mode, the maximum input signal at ANA

IN+ should be 16 mVp-p for optimal signal quali-

ty. The circuit connections for the two modes are

shown in Figure 2 on page 2.

INVERTING ANALOG INPUT (ANA IN–)

This pin is the inverting analog input that transfers

the signal to the device for recording in the dif-

ferential-input mode. In this differential-input

mode, a 16 mVp-p maximum input signal at

ANA IN– should be capacitively coupled to this

pin for optimal signal quality as shown in the ISD

MicroTAD-16M ANA IN Modes, Figure 2. This ca-

pacitor value should be equal to the coupling

capacitor used on the ANA IN+ pin. The input im-

pedance at ANA IN– is nominally 56 KΩ. In the sin-

gle-ended mode, ANA IN– should be

capacitively coupled to VSSA through a capaci-

tor equal to that used on the ANA IN+ input.

AUDIO OUTPUT (AUD OUT)

This pin provides the audio output to the user.

It is capable of driving a 5 KΩ impedance. It is

recommended that this pin be AC coupled.

NOTE

The AUDOUT pin is always at 1.2 volts when

the device is powered up. When in play-

back, the output buffer connected to this

pin can drive a load as small as 5 KΩ. When

in record, a resistor connects AUDOUT to

the internal 1.2 volt analog ground supply.

This resistor is approximately 850 KΩ. This rel-

atively high impedance allows this pin to

be connected to an audio bus without

loading it down.

SLAVE SELECT (SS)

This input, when LOW, will select the ISD Mi-

croTAD-16M device.

MASTER OUT SLAVE IN (MOSI)

This is the serial input to the ISD MicroTAD-16M

device. The master microcontroller places data

on the MOSI line one half-cycle before the rising

clock edge to be clocked in by the ISD Micro-

TAD-16M device.

MASTER IN SLAVE OUT (MISO)

This is the serial output of the ISD MicroTAD-16M

device. This output goes into a high-impedance

state if the device is not selected.

SERIAL CLOCK (SCLK)

This is the clock input to the ISD MicroTAD-16M. It

is generated by the master device (microcon-

troller) and is used to synchronize data transfers

in and out of the device through the MISO and

MOSI lines. Data is latched into the ISD MicroTAD-

16M on the rising edge of SCLK and shifted out of

the device on the falling edge of SCLK.

INTERRUPT (INT)

The ISD MicroTAD-16M interrupt pin goes LOW

and stays LOW when an Overflow (OVF) or End

of Message (EOM) marker is detected. This is an

open drain output pin. Each operation that ends

in an EOM or Overflow will generate an interrupt

including the message cueing cycles. The inter-

rupt will be cleared the next time an SPI cycle is

initiated. The interrupt status can be read by an

RINT instruction.

Overflow Flag (OVF)—The Overflow flag indi-

cates that the end of the ISD MicroTAD-16M’s

analog memory has been reached during a

record or playback operation.

End of Message (EOM)—The End-of-Message

flag is set only during playback operation when

an EOM is found. There are eight EOM flag posi-

tion options per row.

ISD

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