Nuvoton ISD1700 series, Design Manual

Page: 20 / 82

PRELIMINARY ISD1700 SERIES
Publication Release Date: Nov 6, 2008
- 20 - Revision 1.31
REC
. Similarly for play or erase function, pulse
PLAY
or
ERASE
, respectively. Record
source can be either Mic+/- or AnaIn.
•
A subsequent
FWD
operation moves the record and playback pointers to the next SE
sequentially. The LED will also blink one to four times after such operation to indicate
which SE is active. If
FWD
is pressed while in SE4, the LED will flash once to indicate
that SE1 is again active.
•
While the LED is blinking, the device will ignore any input commands. One must wait
patiently until the LED stops blinking completely before any record, play, erase or
forward input should be sent.
8.1.4 Exiting SE Mode
•
The required steps are the same as Entering SE mode. First press and hold
FWD
until
the LED stops blinking (and related SE is played if SEs are programmed). Then,
simultaneously press and hold the
REC
Low until the LED blinks twice (and device will
play SE2 if SE2 is programmed). The device now exits the SE editing mode.
8.1.5 Sound Effect Duration
The duration of SEs is determined by the sampling frequency selected and illustrated in
below table.
Table 8.1 Sound Effect Duration vs. Sampling Frequency
Sampling Frequency 12 kHz 8 kHz 6.4 kHz 5.3 kHz 4 kHz
Duration of SE 0.33 sec 0.5 sec 0.625 sec 0.75 sec 1 sec
8.2 O
PERATION
O
VERVIEW
After power is applied or power-on-reset (POR), the device is in the factory default state and two
internal record and playback pointers are initialized. (These two pointers are discussed later.) Then
the active analog path is determined by the state of the
FT
, the status of the APC register and the
desired operation.
Up to four optional sound effects (SE1~SE4) can be programmed into the device to provide audible
feedback to alert the user about the operating status. Simultaneously, the LED output provides
visual indication about the operating status. During the active state of LED output, no new
command will be accepted.
An unique message management technique is implemented. Under this mode, the recorded
messages are stored sequentially into the embedded memory from the beginning to the end in a
circular fashion automatically.
Two internal pointers, the record pointer and playback pointer, determine the location where an
operation starts. After POR, these pointers are initialized as follows:
•
If no messages are present, both point to the beginning of memory.