ISD MicroTAD-16M
3
ISD
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 K
Ω
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 K
Ω
. In the sin-
gle-ended mode, ANA IN– should be
capacitively coupled to V
SSA
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 K
Ω
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 K
Ω
. When
in record, a resistor connects AUDOUT to
the internal 1.2 volt analog ground supply.
This resistor is approximately 850 K
Ω
. 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.