User guide

Voice Recording & Playback Device Page 7
Revision 2.1
tion as closely as possible:
EXTCLK fre
q = (N) * (128) * (selected sampling frequency)
Example:
Suppose that 8.0 KHz samplin
g is desired. Assume that
the fre
quency of the signal present on EXTCLK = 8MHz.
Roundin
g up, N = 8
The Op Code Parameter bit stream, composed of bits
[A9 - A2][A1 - A0], therefore becomes binar
y
[00001000][10].
The
STOP
Command causes the device to stop the current
operation.
The
STOP_PWDN
command causes the device to stop the
current command and enter power down mode. Durin
g power
down the device consumes si
gnificantly less power. The
PWRUP command must be used to force the device into
power up mode before an
y commands can be executed.
The
SET_REC
command instructs the device to begin
recordin
g at the sector address specified. The device will
continue to record until the end of the current sector is
reached. If no forthcomin
g command has been received
when the end of the sector is reached the device will loop
back to the be
ginning of the same sector and overwrite the
previousl
y recorded material. If the next command is another
SET_REC
or
REC
command the device will execute the com-
mand immediatel
y following the end of the current sector so
that no audio information is lost. For more information see the
section entitled
Recording Audio Data
.
The
REC
command instructs the device to begin recording in
the current sector. If no new command is received before the
device reaches the end of the sector the device will automati-
call
y increment to the next sequential sector and continue
recordin
g. The device will continue to record in this manner
until the memor
y is exhausted or a
STOP
or
STOP_PWDN
command is received. For more information see the section
entitled
Recording Audio Data
.
The
DIG_ERASE
command erases all data contained in the
sector specified. Erase should not be done before recordin
g
voice signals into a sector. Erase must be done before storing
digital data in a sector.
The
DIG_WRITE
command stores 3K bits of digital data in
the specified sector. All 3K bits must be written, no partial
usa
ge of the sector is possible. The memory acts as a FIFO,
the first data bit shifted in will be the first data bit shifted out. A
sector must be erased usin
g the
DIG
_
ERASE
command
BEFORE
data can be written to the sector. For more informa-
tion on storin
g digital data, see the section entitled
Writing
Digital Data
.
The
DIG_READ
command instructs the device to retrieve
di
gital data that was previously written to the specified sector.
The first bit shifted out is the first bit that was written. The last
bit shifted out is the last bit that was written. For more infor-
mation on readin
g digital data see the section entitled
Read-
ing Digital Data.
The
SET_PLAY
command instructs the device to begin play-
back at the specified sector. If no forthcomin
g command is
received, or EOD bit encountered, before the end of the sec-
tor is reached the device will loop back to the be
ginning of the
same sector and continue pla
yback with no noticeable gap in
the audio output. If the next command is another
SET_PLAY
or
PLAY
command the device will execute the command
immediatel
y following the end of the current sector so that no
gap in playback is present. For more information see the sec-
tion entitled
Playing Back Audio Data.
The
PLAY
command instructs the device to begin playback at
the current sector. If no forthcomin
g command is received, or
EOD bit encountered, before the device reaches the end of
the sector the device will automaticall
y increment to the next
se
quential sector and continue playing. The device will con-
tinue to pla
y in this manner until the memory is exhausted or
a
STOP
or
STOP_PWDN
command is received. For more
information see the section entitled
Playing Back Audio Data.
N
8000000
1288000()
--------------------------
7.8125==
APR6008