I1800 SERIES
PIN NAME
ROSC
PIN NO.
19
I/O
I
FUNCTION
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.
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
.
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.
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.
FT
25
I
XCLK
26
RECLED
28
-8-
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