Information
The I
2
S supports both normal and network modes, and these can be selected
independently of whether the transmitter and receiver are synchronous or asynchronous.
Typically, these protocols are used in a periodic manner, where data transfers at regular
intervals, such as at the sampling rate of an external codec. Both modes use the concept
of a frame. The beginning of the frame is marked with a frame sync when programmed
with continuous clock. The RCCR[DC] or TCCR[DC] bits determine the length of the
frame, depending on whether data is being transmitted or received.
The number of words transferred per frame depends on the mode of the I
2
S. In normal
mode, one data word is transferred per frame. In network mode, the frame divides into
two to 32 time slots. In each time slot, one data word is optionally transferred.
Apart from the above basic modes of operation, I
2
S supports the following modes which
require some specific programming.
• I
2
S mode
• AC97 mode
• AC97 fixed mode
• AC97 variable mode
In non-I
2
S slave modes (external frame sync), the I
2
S's programmed word length setting
should be equal to the word length setting of the master. In I
2
S slave mode, the I
2
S's
programmed word length setting can be lesser than or equal to the word length setting of
the I
2
S master (external codec).
In slave modes, the I
2
S's programmed frame length setting (TCCR[DC] or RCCR[DC]
bits) can be lesser than or equal to the frame length setting of the master (external codec).
See Detailed operating mode descriptions for more details on the above modes.
47.2 I
2
S signal descriptions
Table 47-2. I
2
S signal descriptions
Signal Description I/O
SRCK Serial receive clock. SRCK can be used as an input or output.
• In asynchronous mode the receiver uses this clock signal and it is
always continuous.
• In synchronous mode, the STCK port is used instead for clocking in
data.
I/O
Table continues on the next page...
Chapter 47 Integrated interchip sound (I2S)
K10 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc. 1453