
Description of Operation
14-12
ADSP-BF59x Blackfin Processor Hardware Reference
Note most bits shown as a 0 or 1 may be changed depending on the user’s
preference, creating many other “almost standard” modes of stereo serial
operation. These modes may be of use in interfacing to codecs with
slightly non-standard interfaces. The settings shown in
Table 14-2 on
page 14-11
provide glueless interfaces to many popular codecs.
Note
RFSDIV
or
TFSDIV
must still be greater than or equal to
SLEN
. For I
2
S
operation,
RFSDIV
or
TFSDIV
is usually 1/64 of the serial clock rate. With
RSFSE
set, the formulas to calculate frame sync period and frequency (dis-
cussed in
“Clock and Frame Sync Frequencies” on page 14-25
) still apply,
but now refer to one half the period and twice the frequency. For instance,
setting
RFSDIV
or
TFSDIV
= 31 produces an
LRCLK
that transitions every 32
serial clock cycles and has a period of 64 serial clock cycles.
The
LRFS
bit determines the polarity of the
RFS
or
TFS
frame sync pin for
the channel that is considered a “right” channel. Thus, setting
LRFS
= 0
(meaning that it is an active high signal) indicates that the frame sync is
high for the "right" channel, thus implying that it is low for the "left"
channel. This is the default setting.
The
RRFST
and
TRFST
bits determine whether the first word received or
transmitted is a left or a right channel. If the bit is set, the first word
received or transmitted is a right channel. The default is to receive or
transmit the left channel word first.
SLEN
2 – 31
2 – 31
2 – 31
RLSBIT
0
0
0
RFSDIV
(If internal FS is selected.)
2 – Max
2 – Max
2 – Max
RXSE
(Secondary Enable is available for RX and TX.)
X
X
X
Table 14-2. Stereo Serial Settings (Continued)
Bit Field
Stereo Audio Serial Scheme
I
2
S
Left-Justified
DSP Mode
Содержание ADSP-BF59x Blackfin
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