CC2510Fx / CC2511Fx
I2SCLKF2 I2SCLKF1 I2SCLKF0
Fs (kHz)
Word Size (W)
CLKDIV
101.5625
50.78125
9.21201
8.46354
Exact
Yes
Yes
No
8
8
0x06
0x06
0x8A
0x06
0x59
0x59
0x2F
0x59
0x10
0x20
0x1B
0xC0
8
16
16
16
44.1
48
Yes
Table 58: Example I2S Clock Configurations (CC2510Fx, 26 MHz)
12.15.8.2 Word Size
To send mono samples, I2SCFG0.TXMONO
should be set to 1. Each word will then be
repeated in both channels before a new word
is fetched from the data registers. This is to
enable sending a mono audio signal to a
stereo audio sink device.
The word size must be set before master
mode is enabled. The word size is the number
of bits used for each sample and can be set to
a value between 1 and 33. To set the word
size, write word size
–
1
to the
I2SCFG1.WORDS[4:0] bits. Setting the word
size to a value of 17 or more causes the I2S to
pad each word with 0’s in the least significant
bits since the data registers provide maximum
16 bits. This feature allows samples to be sent
to an I2S device that takes a higher resolution
than 16 bits.
12.15.11 Word Counter
The I2S contains a 10-bit word counter, which
is counting transitions on the WS line. The
counter can be cleared by triggers or by writing
to the I2SWCNT register. When a trigger
occurs, or a value is written to I2SWCNT, the
current value of the word counter is copied into
the
If the size of the received samples exceeds 16
bits, only the 16 most significant bits will be put
in the data registers and the remaining low
order bits will be discarded.
I2SSTAT.WCNT[9:8]:I2SWCNT.WCNT[7:0]regi
sters and the word counter is cleared.
Three triggers can be used to copy/clear the
word counter.
12.15.9 Slave Mode
The I2S is configured as a slave device by
setting I2SCFG0.MASTERto 0. When in slave
mode the SCK and WS signals are generated
by an external I2S master and are inputs to the
I2S interface.
• USB SOF: USB Start of Frame. Occurs
every ms (CC2511Fx only)
• T1_CH0: Timer 1, compare, channel 0
• IOC_1: IO pin input transition (P1_3)
Which trigger to use is configured through the
TRIGNUMfield in the I2SCFG1register. When
the I2S is configured not to use any trigger
(I2SCFG1.TRIGNUM=0), the word counter can
only be copied/cleared from software.
12.15.9.1 Word Size
When the I2S operates in slave mode, the word
size is determined by the master that
generates the WS signal.
The I2S will provide bits from the internal 16-bit
buffer until the buffer is empty. If the buffer
becomes empty and the master still requests
more bits, the I2S will send 0’s (low order bits).
The word counter will saturate if it reaches its
maximum value. Software should configure the
trigger-interval and sample-rate to ensure this
never happens.
If more than 16 bits are being received, the low
order bits are discarded.
CC2511Fx: The word counter is typically used to
calculate the average sample rate over a long
period of time (e.g. 1 second) needed by
adaptive isochronous USB endpoints. The
USB SOF event must then be used as trigger.
12.15.10 Mono
The I2S also supports mono audio samples.
12.15.12 µ-Law Compression and Expansion
To receive mono samples, I2SCFG0.RXMONO
should be set to 1. Words from the right
channel will then not be read into the data
registers. This feature is included because
some mono devices repeat their audio data in
both channels and the left channel is the
default mono channel.
The I2S interface can be configured to perform
µ-Law compression and expansion. µ-Law
compression is enabled by setting the
I2SCFG0.ULAWC bit to
1
and µ-Law
SWRS055F
Page 162 of 241
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