PRELIMINARY ISD1700 SERIES
Publication Release Date: Nov 6, 2008
- 30 -
Revision 1.31
4
5
6
7b
4
5
6
7a
: Play : Record : Erase
Erasable
Non-erasable
7b
3
4
5
6
7a
7b
3
4
5
6
7a
7b
8
3
4
5
6
7a
3
4
4
5
7b
3
4
5
6
7a
7b
4
5
6
7a
7b
3
4
5
6
7a
X
RECORD x 3
FWD x 2
RECORD
ERASE
ERASE
FWD x 3
ERASE
ERASE
FWD
4
5
6
4
5
6
7b
4
5
6
7a
7b
4
5
6
7a
: Play : Record : Erase
Erasable
Non-erasable
7b
3
4
5
6
7a
7b
3
4
5
6
7a
7b
3
4
5
6
7a
7b
3
4
5
6
7a
7b
8
3
4
5
6
7a
7b
8
3
4
5
6
7a
3
4
4
5
4
5
7b
3
4
5
6
7a
7b
4
5
6
7a
7b
4
5
6
7a
7b
3
4
5
6
7a
X
RECORD x 3
FWD x 2
RECORD
ERASE
ERASE
FWD x 3
ERASE
ERASE
FWD
Figure 9.2 Further Circular Message Management
A Further example of circular memory management is shown in Figure 9.2. Here note how the three
REC commands cause message 7 to be split across the end of memory boundary. Two FWD
commands will wrap the playback pointer to message four – the second message in the circular
queue. Now if we record until the memory is full, the record pointer becomes invalid and no further
record commands will be accepted by the device. Either the first or last message must be erased first.
The example above demonstrates erasing the last and then the first message as well.
9.1
R
ESTORING
C
IRCULAR
M
EMORY
A
RCHITECTURE
In case the circular memory architecture is damaged, the LED will blink seven times of duration
T
LErr
when either
REC
,
PLAY
,
ERASE
or
FWD
button or alike SPI commands are activated.
During such occurrence, the only way to recover back to an operating status is to perform a
successful global erase operation. In order to perform this effectively, one has to press-and-hold
the
ERASE
for approximately twelve seconds (time for LED to blink seven times plus period for
global erase) at 8 kHz sampling frequency. As a result, the device will resume back to the normal
condition. Details are shown in the related timing diagram.
