Samsung S3C2451X User Manual page 654

IIS-BUS INTERFACE
AUDIO SERIAL DATA FORMAT
IIS-BUS FORMAT
The IIS bus has four lines including serial data input I2SSDI, serial data output I2SSDO, left/right channel select
clock I2SLRCLK, and serial bit clock I2SSCLK; the device generating I2SLRCLK and I2SSCLK is the master.
Serial data is transmitted in 2's complement with the MSB first with a fixed position, whereas the position of the
LSB depends on the word length. The transmitter sends the MSB of the next word at one clock period after the
I2SLRCLK is changed. Serial data sent by the transmitter may be synchronized with either the trailing or the
leading edge of the clock signal. However, the serial data must be latched into the receiver on the leading edge of
the serial clock signal, and so there are some restrictions when transmitting data that is synchronized with the
leading edge.
The LR channel select line indicates the channel being transmitted. I2SLRCLK may be changed either on a
trailing or leading edge of the serial clock, but it does not need to be symmetrical. In the slave, this signal is
latched on the leading edge of the clock signal. The I2SLRCLK line changes one clock period before the MSB is
transmitted. This allows the slave transmitter to derive synchronous timing of the serial data that will be set up for
transmission. Furthermore, it enables the receiver to store the previous word and clear the input for the next word.
MSB (LEFT) JUSTIFIED
MSB-Justified (Left-Justified) format is similar to IIS bus format, except that in MSB-justified format, the transmitter
always sends the MSB of the next word at the same time whenever the I2SLRCLK is changed.
LSB (RIGHT) JUSTIFIED
LSB-Justified (Right-Justified) format is opposite to the MSB-justified format. In other word, the transferring serial
data is aligned with ending point of I2SLRCLK transition.
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
25-4
Specifications and information herein are subject to change without notice.
S3C2451X RISC MICROPROCESSOR