APR6016 Aplus Integrated circuits Inc., APR6016 Datasheet - Page 14

• Manufacturer Part Number: APR6016
• Description: Recording & Playback Voice Ic
• Manufacturer: Aplus Integrated circuits Inc.

The signal returns to a high state after the entire
segment has been played or recorded.
The microprocessor should sense the low edge of
the SAC signal as an indicator that the next
segment needs to be selected, and do so before
the SAC signal returns high.
Failing to specify the next command before the
current segment is exhausted (either during
recording or playback) will result in a noticeable
gap during playback.
The /BUSY pin indicates when the device is
performing either a play, record or fast-forward
function. The host microprocessor can monitor the
busy pin to confirm the status of these commands.
The Busy pin is normally high and goes low while
the length of recording or playback specified by the
user.
Sampling Rate and Voice Quality
The Nyquist Sampling Theorem requires that the
highest frequency component a sampling system
frequency. The APR6016 automatically filters its
input, based on the selected sampling frequency, to
meet this requirement.
Higher sampling rates increase recording
bandwidth,and hence voice quality, but also use
more memory cells for the same amount of
recording time.The APR6016 accommodates
sampling rates as high as 8kHz.Lower sampling
rates use less memory cells and effectively
increase the duration capabilities of the device,
but also reduce recording bandwidth.The APR6016
allows sampling rates as low as 4kHz.
Designers can thus control the quality/duration
trade-off by controlling the sampling frequency.
Sampling frequency can be controlled by the use of
the PWRUP command. This command can change
sampling frequency regardless of whether the
internal oscillator is used or an external clock is
used.
The APR6016 derives its sampling clock from one
of two sources: internal or external. If a clocking
signal is present on the EXTCLK input the device
would automatically use this signal as the sampling
clock source. If no input is present on the EXTCLK
input the device automatically defaults to the
internal clock source.
When the EXTCLK pin is not used it should be tied
to GND.
the device is busy. The low time is governed by
can accommodate without the introduction of
aliasing errors is equal to half the sampling
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An internal clock divider is provided so that
external clock signals can be divided down to a
desired sampling rate. This allows high frequency
signals of up to 10 MHz to be fed into the EXTCLK
pin. Using this feature simplifies designs by
allowing use of a clock already present in the
system, as opposed to having to generate or
externally divide down a custom clock. Details for
programming the clock divider are described in the
SPI
paragraph.
The default power up condition for the APR6016 is
to use the internal oscillator at sampling frequency
of 6.4kHz.
Storage Technology
The APR6016 stores voice signals by sampling
incoming voice data and storing the sampled
signals directly into FLASH memory cells. Each
FLASH cell can support voltage ranges from 1 to
256 levels. These 256 discrete voltage levels are
the equivalent of eight (28=256) bit binary encoded
values. During playback the stored signals are
retrieved from memory, smoothed to form a
continuous signal and finally amplified before
being fed to an external speaker amplifier.
Squelch
The APR6016 is equipped with an internal squelch
feature.
attenuates the output signal by 6dB during quiet
passages in the playback material. Muting the
output signal during quiet passages help to
eliminate background noise.Background noise
may enter the system in a number of ways
including: present in the original signal, natural
noise present in some power amplifier designs, or
induced through a poorly filtered power supply.The
response time of the squelch circuit is controlled
by the time constant of the capacitor connected to
the SQLCAP pin. The recommended value of this
capacitor is 1.0 μF. The squelch feature can be
disabled by the connection of the SQLCAP pin to
VCC.The active low output /SQL goes low
whenever the internal squelch activates. This
signal can be used to squelch the output power
amplifier. Squelching the output amplifier results in
further reduction of noise;especially when the
power amplifier is run at high gain & loud volumes.
interface
The
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Squelch
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APR6016
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PWRUP