Rainbow Electronics ISD1800 - Manual (Page 8)

ISD1800 SERIES
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PIN NAME PIN NO. I/O FUNCTION
V
CCA
, V
CCD
18, 27 Voltage Supplies: Analog and digital circuits
internal to the I1800 device use separate power
buses to minimize noise on the chip. These power
buses are brought out to separate pins on the
package and should be tied together as close to
the power supply as possible. It is important that
the power supply be decoupled as close as
possible to the package.
ROSC 19 I The Resistor Controlled Oscillator input: This
enables the user to vary the I1800 device record
and playback duration. The resistor connected
between the ROSC pin and V
SS
(R2) determines
the sample frequency and the filter upper pass
band for the I1800 device. Please refer to the
table in Duration Section for duration selection.
FT 25 I Feed Through: This mode allows use of the
speaker drivers for external signals. The signal
between the MIC and MIC_REF pins will pass
through the AGC, the filter and the speaker
drivers to the speaker outputs SP+ and SP-. The
input FT controls the feed through mode. To
operate this mode, the control pins REC, PLAYE
and PLAYL are held LOW at V
SS
. The pin FT is
held HIGH to V
CC
. For normal operation of record,
play and power down, the FT pin is held at V
SS
.
The FT pin has a weak pull-down to V
SS
.
XCLK 26 The External Clock input: For the I1800 devices
has an internal pull-down resistor. This pin is
used for test purposes only. Do not bond this pad.
RECLED
28 O
Record LED output: The RECLED output is
LOW during a record cycle. It can be used to
drive an LED to provide feedback that a record
cycle is in progress. In addition, RECLED pulses
LOW momentarily when and End-of-Message
(EOM) or end-of-memory marker is encountered
in a playback cycle.
Note: 1 The REC signal is internally debounced on the rising edge to prevent a false re-triggering from a push-
button switch.