PRELIMINARY ISD1700 SERIES
Publication Release Date: Nov 6, 2008
- 14 -
Revision 1.31
6 FUNCTIONAL DESCRIPTION
6.1 D
ETAILED
D
ESCRIPTION
6.1.1 Audio Quality
Nuvoton’s patented ChipCorder
®
Multi-Level Storage (MLS) technology provides a natural,
high-quality record and playback solution on a single chip. The input voice signals are stored
directly in the Flash memory and are reproduced in their natural form without any of the
compression artifacts caused by digital speech solutions.
6.1.2 Message Duration
The ISD1700 Series offer record and playback duration from 20 seconds to 480 seconds.
Sampling frequency and message duration, T
Dur
, are determined by an external resistor
connected to the R
OSC
pin.
Table 6.1 Duration vs. Sampling Frequency
Sample Freq. ISD1730 ISD1740 ISD1750 ISD1760 ISD1790 ISD17120 ISD17150 ISD17180 ISD17210 ISD17240
12 kHz
20 secs
26 secs
33 secs
40 secs
60 secs
80 secs 100 secs 120 secs 140 secs 160 secs
8 kHz
30 secs
40 secs
50 secs
60 secs
90 secs 120 secs 150 secs 180 secs 210 secs 240 secs
6.4 kHz
37 secs
50 secs
62 secs
75 secs 112 secs 150 secs 187 secs 225 secs 262 secs 300 secs
5.3 kHz
45 secs
60 secs
75 secs
90 secs 135 secs 181 secs 226 secs 271 secs 317 secs 362 secs
4 kHz
60 secs
80 secs 100 secs 120 secs 180 secs 240 secs 300 secs 360 secs 420 secs 480 secs
6.1.3 Flash Storage
The ISD1700 devices utilize embedded Flash memory to provide non-volatile storage. A
message can be retained for a minimum of 100 years without power. Additionally, each
device can be re-recorded over 100,000 times (typical).
6.2 M
EMORY
A
RRAY
A
RCHITECTURE
The memory array provides storage of four special Sound Effects (SEs) as well as the voice data.
The memory array is addressed by rows. A row is the minimum storage resolution by which the
memory can be addressed. The memory assignment is automatically handled by the internal
message management system in standalone mode. While in SPI mode, one has the full access to
the entire memory via the eleven address bits. Table 6.2 shows the minimum storage resolution
with respect to the sampling frequency.
Table 6.2 Minimum Storage Resolution vs. Sampling Frequency
Sampling Frequency
12 kHz
8 kHz
6.4 kHz
5.3 kHz
4 kHz
Minimum Storage Resolution
83.3 msec
125 msec
156 msec
187 msec
250 msec
For example, at 8 kHz sampling frequency, the minimum storage resolution is 125 msec, so each
Sound Effect (SE) is approximately 0.5 second long.
Table 6.3 shows the maximum row address of each device in the ISD1700 family. The four sound
effects (SE) occupy the first sixteen rows in the memory array with four rows for each SE. That
